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TABLE OF CONTENTS
INDEX TO CONSOLIDATED FINANCIAL STATEMENTS

As filed with the Securities and Exchange Commission on October 21, 2010

Registration No. 333-152671

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

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Amendment No. 9
to
FORM S-1
REGISTRATION STATEMENT
UNDER
THE SECURITIES ACT OF 1933

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First Wind Holdings Inc.
(Exact Name of Registrant as Specified in Its Charter)

179 Lincoln Street, Suite 500
Boston, MA 02111
617-960-2888
(Address, Including Zip Code, and Telephone Number, Including Area Code, of Registrant's Principal Executive Offices)

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Paul Gaynor
Chief Executive Officer
First Wind Holdings Inc.
179 Lincoln Street, Suite 500
Boston, MA 02111
617-960-2888
(Name, Address, Including Zip Code, and Telephone Number, Including Area Code, of Agent For Service)

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Copies to:

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Approximate date of commencement of proposed sale to the public:
As soon as practicable after this Registration Statement is declared effective.

          If any securities being registered on this form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, as amended (the "Securities Act"), check the following box.    o

          If this form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.    o

          If this form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.    o

          If this form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.    o

          Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See definitions of "large accelerated filer," "accelerated filer," and "smaller reporting company" in Rule 12b 2 of the Exchange Act. (Check one):

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          The registrant hereby amends this registration statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment which specifically states that this registration statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act or until this registration statement shall become effective on such date as the Commission, acting pursuant to said Section 8(a), may determine.

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The information in this prospectus is not complete and may be changed. We may not sell these securities until the registration statement relating to this prospectus filed with the Securities and Exchange Commission is declared effective. This prospectus is not an offer to sell these securities and it is not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

SUBJECT TO COMPLETION, DATED OCTOBER 21, 2010

12,000,000 Shares

First Wind Holdings Inc.

Class A Common Stock

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        We are offering 12,000,000 shares of our Class A common stock and we intend to use the net proceeds of this offering to repay debt and fund capital expenditures and for general corporate purposes.

        We will be a holding company and our sole asset will be approximately 51.6% of the aggregate Membership Interests of First Wind Holdings, LLC. Concurrently with the completion of this offering, we will issue 12,760,860 and 23,239,140 shares of Class A and Class B common stock, respectively, to members of First Wind Holdings, LLC.

        Before this offering there has been no public market for our Class A common stock. The initial public offering price of our Class A common stock is expected to be between $24.00 and $26.00 per share. We have applied to list our Class A common stock on the Nasdaq Global Market under the symbol "WIND."

        The underwriters have an option to purchase up to 1,800,000 additional shares from us to cover over-allotments, if any.

        Investing in our Class A common stock involves risks. See "Risk Factors" beginning on page 15.

        Delivery of the shares of Class A common stock will be made on or about                       , 2010.

        Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

RBS

The date of this prospectus is                       , 2010.

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OPERATING PROJECTS

        

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        We have not authorized anyone to provide any information or to make any representations other than those contained in this prospectus or in any free writing prospectuses we have prepared. We take no responsibility for, and can provide no assurance as to the reliability of, any information that others may give you. This prospectus is an offer to sell only the shares offered hereby, but only under circumstances and in jurisdictions where it is lawful to do so. The information contained in this prospectus is current only as of its date.

        The service marks for our company name, "FIRST WIND", and our trademark "CLEAN ENERGY. MADE HERE." are the property of First Wind Holdings, LLC. All other trademarks and service marks appearing in this prospectus are the property of their respective holders. All rights reserved.

        In this prospectus, unless the context otherwise requires, we refer to (i) First Wind Holdings Inc. and its subsidiaries, including First Wind Holdings, LLC, after giving effect to the reorganization described herein, as "First Wind," "we," "us," "our" or the "company"; (ii) entities in the D. E. Shaw group as "the D. E. Shaw group;" (iii) Madison Dearborn Capital Partners IV, L.P., as "Madison Dearborn;" and (iv) the D. E. Shaw group and Madison Dearborn collectively as "our Sponsors." We use the following electrical power abbreviations throughout this prospectus: "kW" means kilowatt, or 1,000 watts of electrical power; "MW" means megawatt, or 1,000 kW of electrical power; "GW" means gigawatt, or 1,000 MW of electrical power; "TW" means terawatt, or 1,000 GW of electrical power; and "kWh," "MWh," "GWh" and "TWh" mean an hour during which 1 kW, MW, GW or TW, as applicable, of electrical power has been continuously produced. Capacity refers to rated capacity. References in this prospectus to "NCF" mean net capacity factor, or the measure of a wind energy project's actual production expressed as a percentage of the amount of power the wind energy project could have produced running at full capacity for a particular period of time, and references to "RECs" mean renewable energy certificates or other renewable energy attributes, as the context requires. References to Series B Units in this prospectus are to First Wind Holdings, LLC's Series B Units, which were outstanding prior to the reorganization that will be effected immediately before completion of this offering. Unless otherwise indicated, the financial information in this prospectus represents the historical financial information of First Wind Holdings, LLC.

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PROSPECTUS SUMMARY

        This summary highlights selected information from this prospectus but does not contain all information that you should consider before investing in our Class A common stock. You should read this entire prospectus carefully, including the information under "Risk Factors" beginning on page 15, and the consolidated financial statements included elsewhere in this prospectus.

First Wind Holdings Inc.

        We are an independent wind energy company focused solely on the development, financing, construction, ownership and operation of utility-scale wind energy projects in the United States. Our projects are located in the Northeastern and Western regions of the continental United States and in Hawaii. We have focused on these markets because we believe they provide the potential for future growth and investment returns at the higher end of the range available for wind projects. These markets are characterized by relatively high electricity prices, a shortage of renewable energy and sites with good wind resources that can be built in a cost effective manner. Moreover, we have focused our efforts on projects and regions with significant expansion opportunities, often enabled by transmission solutions that we have developed and built.

        As of September 30, 2010, we operated seven projects with combined rated capacity of 504 MW, and we owned two lines that connect projects to the electricity grid (generator leads) with transmission capacity of approximately 1,200 MW. In 2009, we doubled the number of projects in our operating fleet, adding three new projects with an aggregate capacity of 386 MW. Two of these projects, Milford I, which sells power from Utah into Southern California, and Stetson I, which sells power in New England, include wholly-owned generator leads we had built in anticipation of expanding these projects. In March 2010, we commenced commercial operations of our seventh project, Stetson II, an expansion project in Maine with 26 MW of capacity.

        We manage our business with a team of professionals with experience in all aspects of wind energy development, financing, construction and operations. We have a track record of selecting projects from our development pipeline and converting them into operating projects that we believe will meet our financial return requirements. By the end of 2010, our goal is to have six additional projects with 268 MW of capacity operating or under construction. Four of these projects (totaling 232 MW) are currently under construction: Kahuku (30 MW) in Hawaii, Milford II (102 MW) in the West and Rollins (60 MW) and Sheffield (40 MW) in the Northeast.

        We target having approximately 1,000 MW of projects operating or under construction by the end of 2011. Thereafter, we target adding approximately 200 to 400 MW of operating/under-construction capacity each year to achieve our goal of having an operating/under-construction fleet of approximately 1,900 MW by the end of 2014. Expansions of current operating and under-construction projects make up approximately 32% (measured by capacity) of our targeted 2011-2012 projects. See "Business—Our Development Process" and "Business—Our Portfolio of Wind Energy Projects."

        We believe our development pipeline of approximately 4,000 MW should enable us to meet our 2014 goal of having an operating/under-construction fleet of approximately 1,900 MW. As of September 30, 2010, we had land rights for approximately 80% of our development pipeline and meteorological data for approximately 95% of our development pipeline, in the majority of cases covering at least three years. We have also conducted preliminary environmental screening for all of our projects. We are unlikely to complete all of the projects in our current development pipeline, while some of the projects we are likely to develop in the future are not in our current pipeline. From time to time we have abandoned projects on which we had started development work, or re-categorized projects to a less advanced stage than we had previously assigned them. Our ability to complete our projects and achieve anticipated generation capacities is subject to numerous risks and uncertainties as described under "Risk Factors."

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        Wind energy project returns depend mainly on the following factors: energy prices, transmission costs, wind resources, turbine costs, construction costs, financing costs and availability and government incentives. In applying our strategy, we take into account the combination of all of these factors and focus on margins, return on invested capital and value creation as opposed solely to project size. Some of our projects, while having high construction costs, still offer attractive returns because of favorable wind resources or energy prices. Additionally, in many cases, smaller, more profitable projects can create as much absolute value as do larger, lower-returning projects. We assess the profitability of each project by evaluating its net present value. We also evaluate a project on the basis of its Project EBITDA, as described under "Management's Discussion and Analysis of Financial Condition and Results of Operations—How We Measure Our Performance," including the ratio of Project EBITDA to project development and construction costs.

        We closely manage our commodity price risk and generally construct wind energy projects only if we have put in place some form of a long-term power purchase agreement (PPA) and/or financial hedge. We have PPAs or hedges on all seven of our operating projects and we expect to have PPAs or hedges on all of our 2010 projects. As of September 30, 2010, approximately 90% of the estimated revenues through 2011 from our current operating projects were hedged. We plan to hedge approximately 90% of the estimated revenues for 2011 for the four projects currently under construction and the two projects we plan to have under construction in 2010. Most of the estimated aggregate revenues from our operating projects and 2010 projects is hedged through 2020. See "Business—Revenues; Hedging Activities."

        The United States is one of the largest and fastest growing wind energy markets, although capacity additions have slowed in 2010. As of the end of 2009, the United States was the leading wind energy market in terms of cumulative installed wind power capacity as capacity increased by almost 10 GW, accounting for 39% of all new U.S. electric generating capacity in 2009, according to the American Wind Energy Association (AWEA). Moreover, our markets are among the highest growth U.S. markets due to demand driven by state-mandated renewable portfolio standards (RPS), premium electricity pricing, a shortage of renewable energy and strong wind resources. Based on estimates of IHS Emerging Energy Research (IHS EER), we believe that states in our markets in the Northeast, West and Hawaii will need approximately 42 GW of incremental renewable energy capacity to be built by 2020, assuming a 30% average net capacity factor.

Achievements

        We have achieved a number of milestones, including:

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Northeast.  We completed two of the largest utility-scale wind energy projects in New England (Stetson I and Mars Hill in Maine) and obtained the first permit for a utility-scale wind energy project in Vermont since 1996, our Sheffield project, which is under construction. We built a 200 MW-rated 38-mile 115 kV generator lead in Washington County, Maine as part of our 57 MW Stetson I project. This provides sufficient excess capacity to accommodate up to 140 MW of our expansion projects, including our 26 MW Stetson II project, which commenced commercial operations in March 2010, and our 60 MW Rollins project, which began construction in September 2010. The generator lead interconnects to the ISO-NE market. For our Stetson II project, we have a long-term PPA with Harvard University to sell half of the electricity and RECs generated by the project. See "Business—Our Regions—Northeast."



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West.  We entered into a long-term PPA with the Southern California Public Power Authority (SCPPA) to supply 20 years of power to the cities of Los Angeles, Burbank and Pasadena from Milford I, our 204 MW wind energy project in Utah. This project includes a 1,000 MW generator lead providing transmission to the electricity grid. Milford I commenced commercial operations in November 2009. Milford I is the first wind energy project to receive a grant of a right of way permit under the Bureau of Land Management's (BLM) new programmatic

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environmental impact statement for wind energy development. We have also started construction of Milford II (102 MW) and have capacity on our generator lead for future expansion projects. See "Business—Our Regions—West."

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Hawaii.  We successfully completed and are operating our Kaheawa Wind Power I (KWP I) project in Maui, the largest wind energy project in Hawaii. See "Business—Our Regions—Hawaii." In July 2010, we received from the U.S. Department of Energy (DOE) a $117 million loan guarantee under Section 1703 of the American Recovery and Reinvestment Act of 2009 (ARRA) to help finance construction of our Kahuku project in Oahu. This is the first DOE loan guarantee for a wind energy project. Construction of Kahuku started in July 2010. We also have signed a PPA for our Kaheawa Wind Power II (KWP II) expansion project that is subject to approval by the Hawaii Public Utilities Commission (Hawaiian PUC).



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Financing and U.S. Treasury Grants.  Since the beginning of 2009, in the midst of very difficult financial and credit markets, we have refinanced, raised or received approximately $2.5 billion for our company and projects in 20 refinancing and new capital-raising activities and customer prepayments. These activities included project debt financings, tax equity financings, intermediate holding company financings, government grants, Sponsor equity contributions and customer prepayments. In September 2009, we were among the first recipients of investment tax credit (ITC) cash grants from the U.S. Treasury under Section 1603 of the ARRA and have received approximately $254 million for four of our projects. See "Industry—Drivers of U.S. Wind Energy Growth—State and Federal Government Incentives—American Recovery and Reinvestment Act of 2009 (ARRA)."

Revenues, Financing and Government Programs

        We generate revenues from the sale of electricity and the sale of RECs from our operating projects:

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Electricity sales.  We typically sell the power generated by our projects (sometimes bundled with RECs) either pursuant to PPAs with local utilities or power companies or directly into the local power grid at market prices. Our PPAs have initial terms ranging from five to 20 years with fixed prices, market prices or a combination of fixed and market prices. We also seek to hedge a significant portion of the market component of our power sales revenue with financial swaps. See "Management's Discussion and Analysis of Financial Condition and Results of Operations—Factors Affecting Our Results of Operations, Financial Condition and Cash Flows—Power Purchase Agreements and Financial Hedging."



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REC sales.  The RECs associated with renewable electricity generation can be "unbundled" and sold as separate attributes. In some states, we sell RECs to entities that must either purchase or generate specific quantities of RECs to comply with state or municipal RPS programs. As of September 2010, 25 states and the District of Columbia have adopted RPS programs that operate in tandem with a credit trading system in which generators sell RECs for renewable power they generate.

        We have generated substantial net losses and negative operating cash flows since our inception. See "Risk Factors—Risks Related to Our Business and the Wind Energy Industry—We have generated substantial net losses and negative operating cash flows since our inception and expect to continue to do so as we develop and construct new wind energy projects." In addition, the amount of revenue we generate is subject to fluctuation due to a variety of factors and risks. For example, approximately 10% of our estimated revenue through 2011 from our operating projects is unhedged and is therefore subject to market-price fluctuations. In addition, a significant, long-term decline in market prices for electricity in our markets would adversely affect our un-hedged revenues and make it more difficult for us to develop our projects. Furthermore, the production of wind energy depends heavily on suitable

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wind conditions and if wind conditions are unfavorable, our electricity production and revenue may be substantially below our expectations. See "Risk Factors—Risks Related to Our Business and the Wind Energy Industry."

        We finance our projects with various sources of funds, depending on a project's stage of development and other factors. We use equity, turbine supply loans, construction loans, non-recourse project financings, tax equity financings, term loans and, recently, grants from the U.S. Treasury and a construction and term loan facility guaranteed by the DOE under the ARRA. We are in a capital intensive business and rely heavily on the debt and equity markets to finance the development and construction costs of our projects, and we may not be able to finance the growth of our business. See "Risk Factors—Risks Related to Our Financial Activities."

        We benefit from U.S. government programs established to stimulate the economy and increase domestic investment in the wind energy industry. In February 2009, the ARRA went into effect and extended the federal production tax credit (PTC) for renewable energy generators until the end of 2012. In the past, we have monetized PTCs through tax equity financings as part of our project financing strategy. In these transactions, we receive up-front payments, and our tax equity investors receive most of the operating cash flow and substantially all of the PTCs and taxable income or loss generated by the project until they achieve their targeted investment returns and return of capital, which we typically expect to occur in ten years. As a result, a tax equity financing substantially reduces the cash distributions from the applicable project available to us for other uses. Also, the period during which the tax equity investors receive most of the cash distributions from electricity sales and related hedging activities may last longer than expected if our wind energy projects perform below our expectations.

        The ARRA also made an investment tax credit available to wind energy projects in lieu of PTCs. Project owners can for the first time receive the cash equivalent of the ITC in the form of a grant paid by the U.S. Treasury representing 30% of ITC-eligible costs of building a wind energy project, namely, the costs of constructing energy-producing assets. In September 2009, our Cohocton and Stetson I projects were among the first recipients of such cash grants and have received approximately $254 million for four of our projects. We plan to apply for cash grants for our other 2010 projects. We have also applied for other federal government incentives, including loan guarantees from the DOE. In July 2010, we entered into a $117 million construction and term loan facility guaranteed by the DOE to help finance construction of our Kahuku project. See "Industry—Drivers of U.S. Wind Energy Growth—State and Federal Government Incentives—American Recovery and Reinvestment Act of 2009 (ARRA)."

        We depend heavily on these programs to finance the projects in our development pipeline. If any of these incentives are adversely amended, reduced or eliminated, or if federal departments fail to administer these programs in a timely and efficient manner, it would have a material adverse effect on our ability to obtain financing. Similarly, if governmental authorities stop supporting, or reduce their support for, the development of wind energy projects, our revenues may be adversely affected, our economic return on certain projects may be reduced, our financing costs may increase and it may become more difficult to obtain financing.

Strategy

        Our business strategy is to build a diverse portfolio of operating projects and development opportunities. We seek opportunities where, if we are able to execute successfully, we will be able to generate attractive returns for our stockholders.

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Focus on development of projects in markets with strong demand for renewable energy. We focus on developing projects to serve markets where there is strong demand for renewable energy, including states with RPS programs.

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Develop our existing pipeline of projects and expand existing operating projects. We have identified and are developing a broad pipeline of projects in our markets, including expanding our operating projects in existing locations. We believe expansion projects have lower execution risks than other projects.



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Continue to identify and create a new pipeline of diverse development project opportunities in financially attractive markets. Our team of developers focuses our prospecting and development efforts on identifying new opportunities in our markets and acquiring existing wind energy assets that we believe will meet our financial return requirements in these markets.



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Implement transmission solutions to support development opportunities.  We develop, own and operate generator leads connecting our projects to third-party electricity networks. Our Stetson generator lead has approximately 115 MW of capacity available for our future expansion projects and our Milford generator lead has approximately 750 MW of capacity available for our future expansion projects. Both of these generator leads are operating. We are building our Milford II and Rollins expansion projects using these leads, leaving 700 MW of additional capacity on these lines for our future expansion projects. Our generator lead assets and capabilities enable us to develop projects in areas that would otherwise present significant transmission challenges.



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Focus on construction and operational control.  We believe having control of the construction and operation of our projects enhances our credibility, allows us to make rapid decisions and strengthens our relationships with landowners, local communities, regulators and other stakeholders. For construction projects, we manage and mitigate budget and schedule risks through arrangements with contractors that have significant experience constructing wind energy projects.



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Obtain stable revenues from our operating fleet.  We manage exposure to market prices for electricity through long-term PPAs and hedging. We also seek to maximize the value of the RECs we generate by selling our electricity into markets that have higher RPS requirements and strong markets for RECs. We believe that stabilizing our revenue stream benefits us, our lenders and investors, and enhances our ability to obtain long-term, non-recourse financing for our projects on attractive terms.



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Develop substantial local presence and community stakeholder involvement in our markets. We establish and maintain a local presence early in a project's development to work cooperatively with the communities where our projects are located to more fully understand each community's unique issues and concerns. We believe this helps us to better assess the feasibility of projects and enhances our ability to complete and operate them successfully.

Competitive Strengths

        We intend to use the following strengths to capitalize on what we believe to be significant opportunities for growth in the U.S. wind energy industry in general and in our markets in particular:

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Track record in developing complex wind energy projects.  Our experienced management team has a track record of developing complex projects in each of our three markets. Our project development strategy sometimes includes the construction of generator leads, as in the case of Stetson I and Milford I, or the structuring and negotiation of creative financing and risk management solutions, as in our PPA with SCPPA for Milford I. In certain cases, as in KWP I, we took over projects from other developers who were unable to complete them.



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Ability to finance multiple projects across our portfolio.  Wind energy project development and construction are capital intensive and require access to a relatively constant stream of financing. As a result, our ability to access capital markets efficiently and effectively is crucial to our growth. The recent worldwide financial and credit crisis has reduced the availability of liquidity and credit.

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However, since the beginning of 2009, we have refinanced, raised or received approximately $2.5 billion for our company and projects in 20 refinancing and new capital-raising activities and customer prepayments. These activities included project debt financings, tax equity financings, intermediate holding company financings, government grants, Sponsor equity contributions and customer prepayments. We expect to fund the development of our projects with a combination of cash flows from operations, debt financings, tax equity financings, government grants and capital markets transactions such as this offering. See "Business—Project Financing."

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Established platform in attractive markets with significant growth opportunities.  We have a portfolio of projects in the Northeast, West and Hawaii where we believe we can generate attractive investment returns. These markets are characterized by high electricity prices, a shortage of renewable energy and sites with good wind resources that can be built on cost-effectively. Many of our projects have significant expansion opportunities, which in some cases will enable us to use our existing generator leads. Expansions of our current operating and under-construction projects make up approximately 32% (measured by capacity) of our targeted 2011-2012 projects.



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Well positioned to benefit from over-capacity in the turbine markets because we have few turbine commitments.  Because there is significant over-capacity in the turbine market, we have not entered into firm commitments to purchase turbines for projects in our development pipeline after 2010. We are engaged in a process of seeking requests for proposals from various turbine manufacturers for some of our 2011 and 2012 projects. We also have agreements in place that give us the right, but not the obligation, to purchase additional turbines after 2010, allowing us to cancel our turbine orders with the forfeiture of deposits. We believe this gives us flexibility to acquire turbines at attractive prices and on favorable terms.



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Experienced management team that owns significant equity in the company.  Our management team is experienced in all aspects of the wind energy business. Over the past two years, we have added several key personnel to our team, primarily in the areas of construction, operations and finance. We believe we can achieve our operating/under-construction fleet goal of approximately 1,900 MW by the end of 2014 without significant additions to headcount and overhead costs related to non-operating activities. In addition, members of our senior management team have a meaningful equity stake in our company.

        Our ability to capitalize upon these strengths may be affected by a variety of factors, including competition for: suitable operating sites for projects; access to transmission and distribution networks; turbines and related components at affordable prices; employees with relevant experience; and the limited funds available for tax equity financing.

U.S. Market Opportunity

        According to AWEA, wind energy capacity in the United States grew at a compound annual growth rate (CAGR) of 34% from 2000 through 2009, although capacity additions have slowed in 2010. Wind energy nonetheless accounted for only 1.8% of total U.S. electricity production in 2009 according to the Energy Information Administration (EIA). Based on data provided by IHS EER, we estimate that installed wind capacity in the United States will grow at a CAGR of 19% from 2009 through 2013. In certain U.S. markets, state-mandated RPS and similar voluntary programs, among other factors, have strengthened the demand for renewable energy.

        We believe wind energy growth in the United States is being driven primarily by:

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decreasing costs in the U.S. wind industry supply chain;



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continuing improvements in wind-turbine technologies that increase turbine generating capacity;



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public concern about environmental issues, including climate change;

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favorable federal and state policies regarding climate change and renewable energy, exemplified by state RPS programs and the ARRA, that support the development of renewable energy;



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increasing obstacles for the construction of conventional power plants; and



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public concern over continued U.S. dependence on foreign energy imports.

Risk Factors

        Our business is subject to numerous risks and uncertainties, including:

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those relating to our ability to build our pipeline of projects under development or acquire wind energy assets and turn them into operating projects;



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the impact of schedule delays, cost overruns, revenue shortfalls and lower-than-expected capacity for those projects we do place into operation;



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our substantial net losses and negative operating cash flows;



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government policies supporting renewable energy development;



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our dependence on suitable wind conditions;



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our ability to locate and obtain control of suitable operating sites;



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the need for ongoing access to capital to support our growth;



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our substantial indebtedness and its short-term maturities, which could limit our flexibility in operating our business and to plan for and react to unexpected events; and



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the potential for mechanical breakdowns.

        You should carefully consider all of the information in this prospectus and, in particular, the information under "Risk Factors," prior to making an investment in our Class A common stock.

Class A Common Stock and Class B Common Stock

        After completion of this offering, our outstanding capital stock will consist of Class A common stock and Class B common stock. Investors in this offering will hold shares of Class A common stock. See "Description of Capital Stock."

The Reorganization and Our Holding Company Structure

        First Wind Holdings Inc. was formed for purposes of this offering and has only engaged in activities in contemplation of this offering. Upon completion of the offering, all of our business will continue to be conducted through First Wind Holdings, LLC, which is the holding company that has conducted all of our business to date. First Wind Holdings Inc. will be a holding company, whose principal asset will be its interest in First Wind Holdings, LLC. That interest will represent approximately 51.6% of the economic interests in our business, assuming the underwriters do not exercise their over-allotment option. First Wind Holdings Inc. will be the sole managing member of First Wind Holdings, LLC and will therefore control First Wind Holdings, LLC. Entities in the D. E. Shaw group and Madison Dearborn will collectively own substantially all of the balance of the economic interests in our business. As a holding company, our only source of cash flow from operations will be distributions from First Wind Holdings, LLC. See "The Reorganization and Our Holding Company Structure." After completion of this offering, First Wind Holdings Inc. will be a "controlled company" under the listing rules of the Nasdaq Stock Market (Nasdaq Listing Rules).

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        The diagram below shows our organizational structure immediately after completion of this offering and related transactions, assuming no exercise of the underwriters' over-allotment option.

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(1)

Certain entities in the D. E. Shaw group will receive Class A common stock rather than Series B Membership Interests (and the corresponding shares of Class B common stock). As a result, the D. E. Shaw group will hold a combination of Series B Membership Interests, Class A common stock and Class B common stock. The Class A common stock held by the D. E. Shaw group will have 48.0% of the voting power, and 25.6% of the economic rights, in First Wind Holdings Inc. if the underwriters exercise their over-allotment option in full. On a combined basis, the Class A common stock and Class B common stock held by the D. E. Shaw group will represent combined voting power of 35.3% in First Wind Holdings Inc. (or 34.0% if the underwriters exercise their over-allotment option in full).

(2)

The members of First Wind Holdings, LLC, other than us, will consist of our Sponsors and certain of our employees and current investors in First Wind Holdings, LLC.

(3)

The Class A common stockholders will have the right to receive all distributions made on account of our capital stock. Each share of Class A common stock and Class B common stock is entitled to one vote per share. The Class A common stock held by public stockholders will have 27.7% of the voting power, and 52.0% of the economic rights, in First Wind Holdings Inc. if the underwriters exercise their over-allotment option in full.

(4)

46.7% of the voting power in First Wind Holdings Inc. if the underwriters exercise their over-allotment option in full.

(5)

Series A Membership Interests and Series B Membership Interests will have the same economic rights in First Wind Holdings, LLC. Series A and Series B Membership Interests will have 53.3% and 46.7%, respectively, of the economic rights in our business through First Wind Holdings, LLC if the underwriters exercise their over-allotment option in full.

Corporate Information

        We began developing wind energy projects in North America in 2002. First Wind Holdings Inc. was incorporated in Delaware in May 2008. Our principal executive offices are located at 179 Lincoln Street, Suite 500, Boston, Massachusetts 02111, and our telephone number is (617) 960-2888. Our website is www.firstwind.com. The information contained on or accessible through our website, or any other website referenced in this prospectus, is not part of this prospectus and you should not consider it in making an investment decision.

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The Offering

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        The number of shares to be outstanding after completion of this offering is based on 12,760,860 shares of Class A common stock and 23,239,140 shares of Class B common stock outstanding as of October 20 after giving effect to the reorganization described under "The Reorganization and Our Holding Company Structure." The number of shares to be outstanding after this offering excludes 5,500,000 additional shares of Class A common stock reserved for issuance under our long-term incentive plan.

        Unless we specifically state otherwise, the information in this prospectus assumes:

•

the implementation of the reorganization described in "The Reorganization and Our Holding Company Structure;" and



•

no exercise of the underwriters' over-allotment option.

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Summary Financial and Operating Data

        The following tables present summary consolidated financial data as of and for the dates and periods indicated below. The summary consolidated statement of operations data for the years ended December 31, 2007, 2008 and 2009 and the summary consolidated balance sheet data as of December 31, 2008 and 2009 are derived from our audited consolidated financial statements included elsewhere in this prospectus. The summary consolidated statement of operations data for the nine months ended September 30, 2009 and 2010 and the summary consolidated balance sheet data as of September 30, 2010 are derived from our unaudited interim consolidated financial statements included elsewhere in this prospectus. The unaudited interim period financial information, in the opinion of management, includes all adjustments, which are normal and recurring in nature, necessary for the fair presentation of the periods shown.

        The summary unaudited pro forma consolidated financial data for the year ended December 31, 2009 and for the nine months ended September 30, 2010 have been prepared to give pro forma effect to all of the reorganization transactions described in "The Reorganization and Our Holding Company Structure" and this offering as if they had been completed as of January 1, 2009 with respect to the unaudited consolidated pro forma statement of operations and as of September 30, 2010 with respect to the unaudited pro forma consolidated balance sheet data. These data are subject and give effect to the assumptions and adjustments described in the notes accompanying the unaudited pro forma financial statements included elsewhere in this prospectus. The summary unaudited pro forma financial data are presented for informational purposes only and should not be considered indicative of actual results of operations that would have been achieved had the reorganization transactions and this offering been consummated on the dates indicated, and do not purport to be indicative of statements of financial condition data or results of operations as of any future date or for any future period. Pro forma net loss per share is based on the weighted average common shares outstanding.

        The summary consolidated financial data set forth below should be read in conjunction with the "Unaudited Pro Forma Financial Information," "Selected Historical Financial and Operating Data," "Management's Discussion and Analysis of Financial Condition and Results of Operations" and the consolidated financial statements and related notes included elsewhere in this prospectus. Our historical results may not be indicative of the operating results to be expected in any future period.

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(1)

The basic net loss attributable per common unit for each of the annual periods ended December 31, 2007, 2008 and 2009 and the nine month periods ended September 30, 2009 and 2010 has been presented for informational and historical purposes only. After completion of this offering, as a result of the reorganization events that have taken place or that will take place immediately prior to completion of the offering as described in "The Reorganization and Our Holding Company Structure," the shares used in computing net earnings or loss per share will bear no relationship to these historical common units.

Pro forma basic and diluted net loss per share was computed by dividing the pro forma net loss attributable to our Class A common stockholders by the shares of Class A common stock that we will issue and sell in this offering, plus shares issued in connection with our initial capitalization, assuming that these shares of Class A common stock were outstanding for the entirety of each of the historical periods presented on a pro forma basis. No pro forma effect was given to the future potential exchanges of the Series B Membership Interests of our subsidiary, First Wind Holdings, LLC (and the equal number of shares of our Class B common stock), that will be outstanding immediately after the completion of this offering and the reorganization transactions for an equal number of shares of our Class A common stock because the issuance of shares of Class A common stock upon these exchanges would not be dilutive.

(2)

Operating cash flows for the nine months ended September 30, 2010 include a prepayment for energy for our Milford I project of approximately $232 million.

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(3)

Average realized energy price per MWh of energy generated is a metric that allows us to compare revenues from period to period, or on a project by project basis, regardless of whether the revenues are generated under a PPA, from sales at market prices with a financial swap, from sales at market prices or a combination of the three. Although average realized energy price is based, in part, on revenues recognized under accounting principles generally accepted in the United States (GAAP), this metric does not represent revenue per unit of production on a GAAP basis. We adjust GAAP revenues used to compute this metric in several respects:

•

Under GAAP, recognition of revenues from the sale of New England RECs is delayed due to regulations that limit their transfer to the buyer to quarterly trading windows that open two quarters subsequent to generation. To match New England REC revenue to the period in which the related power was generated, in calculating this metric, we add New England REC revenues attributable to generation during a period but not yet recognized under GAAP, and subtract New England REC revenue recognized under GAAP in the period but generated in a prior period.

•

In addition, in order to focus this metric on realized energy prices, we exclude the effects of mark-to-market adjustments on financial swaps.

Average realized energy price changes over time due to several factors. Historically, the most significant factor has been the growth of our business and the corresponding change in pricing mix. Each project has a different pricing profile, including varying levels of hedging in relation to electricity generation, and in certain cases, short periods of unhedged exposure to market price fluctuations as hedging agreements are put in place.

The table below shows the calculation of our average realized energy price for the periods presented:

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(a)

New England REC timing represents the difference between: (i) New England RECs generated in earlier periods that qualified for GAAP revenue recognition in the applicable period and (ii) New England RECs generated in the applicable period and sold to a counterparty under a firm sales contract where revenue is deferred under GAAP until the applicable quarterly trading window occurs. The gross amounts of such New England RECs are as follows:

(b)

The mark-to-market adjustments for the 2009 periods include the effect of a financial hedge modification fee of $4,147 in addition to market adjustments of $17,175 and $19,192 for the year and the nine months, respectively.

(4)

We evaluate the performance of our operating projects on the basis of their Project EBITDA, which is a non-GAAP financial measure. We use Project EBITDA to assess the performance of our operating projects because we believe it is a measure that allows us to: (i) more accurately evaluate the operating performance of our projects based on the energy generated during each period (through the exclusion of mark-to-market adjustments and the effects of New England REC timing, for which the GAAP accounting treatment does not correspond to the energy generated during the period) and (ii) assess the ability of our projects to support debt and/or tax equity financing (through the exclusion of depreciation and amortization that is not indicative of capital costs that would be expected over the term of the financing and general and administrative expenses that are not incurred at the project level). Our ability to raise debt and/or tax equity financing for our projects is a key requirement of our development plan as described in "—Factors Affecting Our Results of Operations, Financial Condition and Cash Flows—Financing Requirements." We believe it is important for investors to understand the factors that we focus on in managing the business, and therefore we believe Project EBITDA is useful for investors to understand. In addition, as long as investors consider Project EBITDA in combination with the most directly comparable GAAP measure, gross income (loss), we believe it is useful for investors to have information about our operating

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performance on a period-by-period basis, without giving effect to GAAP requirements that require the recognition of income or expense that does not correspond to actual energy production in a given period, and we believe it is useful for investors to consider a measure that does not include project-related depreciation and amortization. Because lenders and providers of tax equity financing frequently disregard the non-cash charges and GAAP timing differences noted above when determining the financeability of a project, we believe that presenting information in this manner can help give investors an understanding of our ability to secure financing for our projects. Project EBITDA can be reconciled to gross income (loss), which we believe to be the most directly comparable financial measure calculated and presented in accordance with GAAP, as follows (in thousands):

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(a)

The mark-to-market adjustments for the 2009 periods include the effect of a financial hedge modification fee of $4,147 in addition to market adjustments of $17,175 and $19,192 for the year and the nine months, respectively.



(b)

In June 2010, the County of Maui, Hawaii retroactively assessed property taxes for our KWP I project totaling approximately $1.4 million plus penalties and interest for 2007, 2008 and 2009. We have appealed these retroactive assessments as well as the amount then billed by the county for 2010. The KWP I property tax assessment adjustment reflects these retroactive assessments in the periods to which they relate.

Project EBITDA does not represent funds available for our discretionary use and is not intended to represent or to be used as a substitute for gross income (loss), net income or cash flow from operations data as measured under GAAP. We use Project EBITDA to assess the performance of our operating projects and not as a measure of our liquidity. Investors should consider cash flow from operations, and not Project EBITDA, when evaluating our liquidity and capital resources. The items excluded from Project EBITDA are significant components of our statement of operations and must be considered in performing a comprehensive assessment of our overall financial performance. Project EBITDA and the associated period-to-period trends should not be considered in isolation.

        The following table presents summary consolidated balance sheet data as of the dates indicated:

•

on an actual basis;



•

on a pro forma basis as of September 30, 2010 to give effect to all of the reorganization transactions described in "The Reorganization and Our Holding Company Structure"; and



•

on a pro forma as adjusted basis as of September 30, 2010 to give further effect to our sale of 12,000,000 shares of common stock in this offering at an assumed initial public offering price of $25.00 per share, the midpoint of the range set forth on the cover of this prospectus, after deducting estimated underwriting discounts and commissions and estimated offering expenses.

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RISK FACTORS

        You should consider carefully each of the risks described below, together with all of the other information contained in this prospectus, before deciding to invest in our Class A common stock. If any of the following risks materializes, our business, financial condition and results of operations may be materially adversely affected. In that event, the trading price of our Class A common stock could decline, and you could lose some or all of your investment.

        This prospectus also contains forward-looking statements that involve risks and uncertainties. Actual results could differ materially from those anticipated in these forward-looking statements as a result of various factors, including the risks described below and elsewhere in this prospectus. See "Cautionary Statement Regarding Forward-Looking Statements."

Risks Related to Our Business and the Wind Energy Industry

If we cannot continue to build our pipeline of projects under development and turn them into operating projects, our business will not grow and we may have significant write-offs.

        We may be unable to meet our target of having approximately 1,900 MW of operating/under-construction capacity by 2014, because we will need to add new projects to our pipeline on an ongoing basis, including projects we acquire from others. In addition, we may have difficulty in converting our development pipeline into operating projects or may be unable to find suitable projects to add to our pipeline. These circumstances could prevent those projects from commencing operations or from meeting our original expectations about how much energy they will generate or the returns they will achieve. Since completing the projects in or added to our development pipeline as anticipated or at all involves numerous risks and uncertainties, some projects in our portfolio will not progress to construction or may be substantially delayed. From time to time we have abandoned projects on which we had started development work, or re-categorized projects to a less advanced stage than we had previously assigned them, representing in the aggregate approximately 145 MW of potential capacity. This resulted in $3.5 million, $3.1 million and $2.5 million of write-offs in 2008, 2009 and the nine months ended September 30, 2010, respectively. Abandonment or re-categorization of our projects may make it difficult for us to achieve our capacity goals by our target dates. As we increase our development activities and the number of projects in our pipeline, such discontinuations and re-categorizations and the corresponding write-offs may increase. In addition, those projects that are constructed and begin operations may not meet our return expectations due to schedule delays, cost overruns or revenue shortfalls or they may not generate the capacity that we anticipate or result in receipt of revenue in the originally anticipated time period or at all. An inability to maintain and add to our development pipeline or to convert projects into financially successful operating projects would have a material adverse effect on our business, financial condition and results of operations.

We have generated substantial net losses and negative operating cash flows since our inception and expect to continue to do so as we develop and construct new wind energy projects.

        We have generated substantial net losses and negative operating cash flows from operating activities since our operations commenced. We had accumulated losses of approximately $233.0 million from our inception through September 30, 2010. For the year ended December 31, 2009 and the nine months ended September 30, 2010, we generated net losses of $61.0 million and $52.0 million, respectively. In addition, our operating activities used cash of $54.5 million for the year ended December 31, 2009 and $28.5 million (excluding the $232.0 million prepayment for energy for our Milford I project) for the nine months ended September 30, 2010.

        We expect that our net losses will continue and our cash used in operating activities will grow during the next several years, as compared with prior periods, as we increase our development activities and construct additional wind energy projects. Wind energy projects in development typically incur operating losses prior to commercial operation at which point the projects begin to generate positive

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operating cash flow. We also expect to incur additional costs, contributing to our losses and operating uses of cash, as we incur the incremental costs of operating as a public company. Our costs may also increase due to such factors as higher than anticipated financing and other costs; non-performance by third-party suppliers or subcontractors; increases in the costs of labor or materials; and major incidents or catastrophic events. If any of those factors occurs, our net losses and accumulated deficit could increase significantly and the value of our common stock could decline.

We depend heavily on federal, state and local government support for renewable energy, especially wind projects.

        We depend heavily on government policies that support renewable energy and enhance the economic feasibility of developing wind energy projects. The federal government and several of the states in which we operate or into which we sell power provide incentives that support the sale of energy from renewable sources, such as wind.

        The Internal Revenue Code provides a production tax credit (PTC) for each kWh of energy generated by an eligible resource. Under current law, an eligible wind facility placed in service prior to the end of 2012 may claim the PTC. The PTC is a credit claimed against the income of the owner of the eligible project.

        PTC eligible projects are also eligible for an investment tax credit (ITC) of 30% of the eligible cost-basis, which is in lieu of the PTC. The same placed-in-service deadline of December 31, 2012 applies for purposes of the ITC. The ITC is a credit claimed against the income of the owner of the eligible project.

        The American Recovery and Reinvestment Act of 2009 (ARRA) created a grant administered by the U.S. Treasury that provides for a cash payment of the amount an eligible project whose construction began in 2010 would otherwise be able to claim under the ITC. In addition, there are various programs for loan guarantees. See "Industry—Drivers of U.S. Wind Energy Growth—State and Federal Government Incentives."

        In addition to federal incentives, we rely on state incentives that support the sale of energy generated from renewable sources, including state adopted renewable portfolio standards (RPS) programs. Such programs generally require that electricity supply companies include a specified percentage of renewable energy in the electricity resources serving a state or purchase credits demonstrating the generation of such electricity by another source. However, the legislation creating such RPS requirements usually grants the relevant state public utility commission the ability to reduce electric supply companies' obligations to meet the RPS requirements in certain circumstances. If the RPS requirements are reduced or eliminated, this could result in our receiving lower prices for our power and in a reduction in the value of our RECs, which could have a material adverse effect on us. See "Industry—Drivers of U.S. Wind Energy Growth—State and Federal Government Incentives."

        We depend heavily on these programs to finance the projects in our development pipeline. If any of these incentives are adversely amended, eliminated, subjected to new restrictions, not extended beyond their current expiration dates, or if funding for these incentives is reduced, it would have a material adverse effect on our ability to obtain financing. A delay or failure by governmental authorities to administer these programs in a timely and efficient manner could have a material adverse effect on our financing.

        While certain federal, state and local laws, programs and policies promote renewable energy and additional legislation is regularly being considered that would enhance the demand for renewable energy, they may be adversely modified, legislation may not pass or may be amended and governmental support of renewable energy development, particularly wind energy, may not continue or may be reduced. If governmental authorities do not continue supporting, or reduce or eliminate their support

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for, the development of wind energy projects, our revenues may be adversely affected, our economic return on certain projects may be reduced, our financing costs may increase, it may become more difficult to obtain financing, and our business and prospects may otherwise be adversely affected.

Most of our revenue comes from sales of electricity and RECs, which are subject to market price fluctuations, and there is a risk of a significant, sustained decline in their market prices. Such a decline may make it more difficult to develop our projects.

        We may not be able to develop our projects economically if there is a significant, sustained decline in market prices for electricity or RECs without a commensurate decline in the cost of turbines and the other capital costs of constructing wind energy projects. Electricity prices are affected by various factors and may decline for many reasons that are not within our control. Those factors include changes in the cost or availability of fuel, regulatory and governmental actions, changes in the amount of available generating capacity from both traditional and renewable sources, changes in power transmission or fuel transportation capacity, seasonality, weather conditions and changes in demand for electricity. In addition, other power generators may develop new technologies or improvements to traditional technologies to produce power that could increase the supply of electricity and cause a sustained reduction in market prices for electricity and RECs. If governmental action or conditions in the markets for electricity or RECs cause a significant, sustained decline in the market prices of electricity or those attributes, without an offsetting decline in the cost of turbines or other capital costs of wind energy projects, we may not be able to develop and construct our pipeline of development projects or achieve expected revenues, which could have a material adverse effect on our business, financial condition and results of operations.

The production of wind energy depends heavily on suitable wind conditions. If wind conditions are unfavorable or below our estimates, our electricity production, and therefore our revenue, may be substantially below our expectations.

        The electricity produced and revenues generated by a wind energy project depend heavily on wind conditions, which are variable and difficult to predict. Operating results for projects vary significantly from period to period depending on the windiness during the periods in question. We base our decisions about which sites to develop in part on the findings of long-term wind and other meteorological studies conducted in the proposed area, which measure the wind's speed, prevailing direction and seasonal variations. Actual wind conditions, however, may not conform to the measured data in these studies and may be affected by variations in weather patterns, including any potential impact of climate change. Therefore, the electricity generated by our projects may not meet our anticipated production levels or the rated capacity of the turbines located there, which could adversely affect our business, financial condition and results of operations. In recent years and in the first quarter of 2010, the wind resources at our operating projects, while within the range of our long-term estimates, varied from the averages we expected. If the wind resources at a project are below the average level we expect, our rate of return for the project would be below our expectations and we would be adversely affected. Projections of wind resources also rely upon assumptions about turbine placement, interference between turbines and the effects of vegetation, land use and terrain, which involve uncertainty and require us to exercise considerable judgment. We or our consultants may make mistakes in conducting these wind and other meteorological studies. Any of these factors could cause us to develop sites that have less wind potential than we expected, or to develop sites in ways that do not optimize their potential, which could cause the return on our investment in these projects to be lower than expected.

        If our wind energy assessments turn out to be wrong, our business could suffer a number of material adverse consequences, including:

•

our energy production and sales may be significantly lower than we predict;

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our hedging arrangements may be ineffective or more costly;



•

we may not produce sufficient energy to meet our commitments to sell electricity or RECs and, as a result, we may have to buy electricity or RECs on the open market to cover our obligations or pay damages; and



•

our projects may not generate sufficient cash flow to make payments of principal and interest as they become due on our project-related debt, and we may have difficulty obtaining financing for future projects.

Natural events may reduce energy production below our expectations.

        A natural disaster, severe weather or an accident that damages or otherwise adversely affects any of our operations could have a material adverse effect on our business, financial condition and results of operations. Lightning strikes, blade icing, earthquakes, tornados, extreme wind, severe storms, wildfires and other unfavorable weather conditions or natural disasters could damage or require us to shut down our turbines or related equipment and facilities, impeding our ability to maintain and operate our facilities and decreasing electricity production levels and our revenues. Operational problems, such as degradation of turbine components due to wear or weather or capacity limitations on the electrical transmission network, can also affect the amount of energy we are able to deliver. Any of these events, to the extent not fully covered by insurance, could have a material adverse effect on our business, financial condition and results of operations.

Operational problems may reduce energy production below our expectations.

        Spare parts for wind turbines and key pieces of electrical equipment may be hard to acquire or unavailable to us. Sources for some significant spare parts and other equipment are located outside of North America. If we were to experience a shortage of or inability to acquire critical spare parts, we could incur significant delays in returning facilities to full operation. In addition, we generally do not hold spare substation main transformers. These transformers are designed specifically for each wind energy project, and the current lead time to receive an order for this type of equipment is over eight months. For example, operations at our Stetson I project were temporarily interrupted in February 2010 due to a transformer malfunction. If we had to replace any of our substation main transformers, we could be unable to sell electricity from the affected wind energy project until a replacement is installed. That interruption to our business might not be fully covered by insurance.

One of our key turbine suppliers, Clipper Windpower Plc, has experienced certain technical issues with its wind turbine technology and may continue to experience similar issues.

        Clipper, one of our two turbine suppliers in our existing operating fleet, entered the wind turbine market in 2007. Clipper's first prototype wind turbine, the 2.5 MW Liberty, was placed in service in April 2005. We now operate 116 Liberty turbines (290 MW) and plan to install 34 Liberty turbines in 2010 (85 MW). We have entered into agreements which provide us the right but not the obligation to acquire up to 253 Liberty turbines (633 MW) for installation during 2011-2015. We deployed the first eight commercially produced Liberty turbines at our Steel Winds I project, which commenced commercial operations on June 1, 2007. Since our initial deployment, Clipper has announced and remediated three defects affecting the Liberty turbines deployed by us and other customers that resulted in prolonged downtime for turbines at various projects, including our Steel Winds I and Cohocton projects. Among issues adversely affecting Liberty turbine performance were drive trains that incorporated a supplier-related deficiency, a design deficiency resulting in separation of bonding materials in the blades of several turbines and minor defects in the blade skin resulting from a defective manufacturing process. At present, all such items affecting our installed Clipper fleet have been remediated and average availability of the Liberty turbines in our fleet through 2010 is within warranted levels.

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        The Liberty turbines, however, may not perform in accordance with Clipper's specifications for their anticipated useful life or may require additional warranty or non-warranty repairs. In addition, the initial failure of performance has adversely affected our ability to arrange and close turbine supply loans, tax equity financing transactions and construction loans involving Liberty turbines. Moreover, Clipper may not be able to fund its obligations to us and its other customers under its outstanding warranty agreements.

        A failure of Clipper to produce Liberty turbines that perform within design specifications would preclude us from completing projects that could otherwise incorporate Clipper technology and likely result in our determination to elect not to purchase any or all Liberty turbines that we have the right but not the obligation to acquire from 2011 through 2015.

        We have paid Clipper approximately $60 million in deposits and progress payments towards turbine purchases from 2011–2015 and intend to pay approximately $30 million more in deposits and progress payments through January 15, 2011. If we elect for any reason not to acquire any additional turbines from Clipper, we will forfeit the pro rata portion of these deposits and progress payments corresponding to the schedule of future turbine purchases: $38.6 million for turbines scheduled to be purchased in 2011, $17.9 million for 2012, $10.7 million for 2013, $13.4 million for 2014 and $8.9 million for 2015.

        We have no commitments from turbine manufacturers other than Clipper for projects we plan to have in construction after 2010.

A portion of our revenues from the sale of RECs is not hedged, and we are exposed to volatility of commodity prices with respect to those sales.

        REC prices are driven by various market forces, including electricity prices and the availability of electricity from other renewable energy sources and conventional energy sources. We are unable to hedge a portion of our revenues from RECs in certain markets where conditions limit our ability to sell forward all of our RECs. Our ability to hedge RECs generated by our Northeast projects is limited by the unbundled nature of the RECs and the relative illiquidity of this market, and revenues associated with these RECs account for a majority of the unhedged revenue stream from our existing operating fleet. We are exposed to volatility of commodity prices with respect to the portion of RECs that are unhedged, including risks resulting from changes in regulations, including state RPS targets, general economic conditions and changes in the level of renewable energy generation. We expect to have quarterly variations in our revenues from the sale of unhedged RECs.

We have a limited operating history and our rapid growth may make it difficult for us to manage our business efficiently.

        Since we began our business in 2002 and began commercial operation of our first wind energy project in 2006, there is limited history to use to evaluate our business. You should consider our prospects in light of the risks and uncertainties growing companies encounter in rapidly evolving industries such as ours. Also, our rapid growth may make it difficult for us to manage our business efficiently, effectively manage our capital expenditures and control our costs, including general and administrative costs. These challenges could have a material adverse effect on our business, financial condition and results of operation.

We rely on a limited number of key customers.

        There are a limited number of possible customers for electricity and RECs produced in a given geographic location. As a result, we do not have many choices about the buyers of our electricity, which limits our ability to negotiate the terms under which we sell electricity. Also, since we depend on sales of electricity and RECs to certain key customers, our operations are highly dependent upon these customers' fulfilling their contractual obligations under our power purchase agreements (PPAs) and

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other material sales contracts. For example, 45% of our revenues were generated from sales of electricity under PPAs with four customers in the year ended December 31, 2009. Our customers may not comply with their contractual payment obligations or may become subject to insolvency or liquidation proceedings during the term of the relevant contracts. In addition, the credit support we received from such customers to secure their payments under the PPAs may not be sufficient to cover our losses if they fail to perform. To the extent that any of our customers are, or are controlled by, governmental entities, they may also be subject to legislative or other political action that impairs their contractual performance. Failure by any key customer to meet its contractual commitments or insolvency or liquidation of our customers could have a material adverse effect on our business, financial condition and results of operations.

We face competition primarily from other renewable energy sources and, in particular, other wind energy companies.

        We believe our primary competitors are developers and operators focused on renewable energy generation, and specifically wind energy companies. Renewable energy sources, including wind, biomass, geothermal and solar, currently benefit from various governmental incentives such as PTCs, ITCs, cash grants, loan guarantees, RPS programs and accelerated tax depreciation. Changes in any of these incentives could significantly disadvantage wind energy generators including us, compared with other renewable energy sources. Further, the energy industry is rapidly evolving and highly competitive. A reduction in demand for energy from renewable sources or our failure to identify and adapt to new technologies could have a material adverse effect on our business, financial condition and results of operations.

        We compete with other wind energy companies primarily for sites with good wind resources that can be built in a cost-effective manner. We also compete for access to transmission or distribution networks. Because the wind energy industry in the United States is at an early stage, we also compete with other wind energy developers for the limited pool of personnel with requisite industry knowledge and experience. Furthermore, in recent years, there have been times of increased demand for wind turbines and their related components, causing turbine suppliers to have difficulty meeting the demand. If these conditions return in the future, turbine and other component manufacturers may give priority to other market participants, including our competitors, who may have resources greater than ours.

        We compete with other renewable energy companies (and energy companies in general) for the financing needed to pursue our development plan. Once we have developed a project and put a project into operation, we may compete on price if we sell electricity into power markets at wholesale market prices. Depending on the regulatory framework and market dynamics of a region, we may also compete with other wind energy companies, as well other renewable energy generators, when we bid on or negotiate for a long-term PPA.

We also compete with traditional energy companies.

        We also compete with traditional energy companies. For example, depending on the regulatory framework and market dynamics of a region, we also compete with traditional electricity producers when we bid on or negotiate for a long-term PPA. Furthermore, technological progress in traditional forms of electricity generation (including technology that reduces or sequesters greenhouse gas emissions) or the discovery of large new deposits of traditional fuels could reduce the cost of electricity generated from those sources or make them more environmentally friendly, and as a consequence reduce the demand for electricity from renewable energy sources or render existing or future wind energy projects uncompetitive. Any of these developments could have a material adverse effect on our business, financial condition and results of operations.

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The growth of our business depends on locating and obtaining control of suitable operating sites.

        Wind energy projects require wind conditions that are found in limited geographic areas and, within these areas, at particular sites. These sites must also be suitable for construction of a wind energy project, including related roads and operations and maintenance facilities. Further, projects must be interconnected to electricity transmission or distribution networks. Once we have identified a suitable operating site, obtaining the requisite land rights (including access rights, setbacks and other easements) requires us to negotiate with landowners and local government officials. These negotiations can take place over a long time, are not always successful and sometimes require economic concessions not in our original plans. The property rights necessary to construct and interconnect our projects must also be insurable and otherwise satisfactory to our financing counterparties. In addition, our ability to obtain adequate property rights is subject to competition from other wind energy developers. If a competitor or other party obtains land rights critical to our project development efforts that we are unable to resolve, we could incur losses as a result of development costs for sites we do not develop, which we would have to write off. If we are unable to obtain adequate property rights for a project, including its interconnection, that project may be smaller in size or potentially unfeasible. Failure to obtain insurable property rights for a project satisfactory to our financing counterparties would preclude our ability to obtain third-party financing and could prevent ongoing development and construction of that project.

Negative public or community response to wind energy projects in general or our projects specifically can adversely affect our ability to develop our projects.

        Negative public or community response to wind energy projects in general or our projects specifically can adversely affect our ability to develop, construct and operate our projects. This type of negative response can lead to legal, public relations and other challenges that impede our ability to meet our development and construction targets, achieve commercial operations for a project on schedule, address the changing needs of our projects over time and generate revenues. Some of our projects are and have been the subject of administrative and legal challenges from groups opposed to wind energy projects in general or concerned with potential environmental, health or aesthetic impacts, impacts on property values or the rewards of property ownership, or impacts on the natural beauty of public lands. We expect this type of opposition to continue as we develop and construct our existing and future projects. An increase in opposition to our requests for permits or successful challenges or appeals to permits issued to us could materially adversely affect our development plans. If we are unable to develop, construct and operate the production capacity that we expect from our development projects in our anticipated timeframes, it could have a material adverse effect on our business, financial condition and results of operations.

We need governmental approvals and permits, including environmental approvals and permits, to construct and operate our projects. Any failure to procure and maintain necessary permits would adversely affect ongoing development, construction and continuing operation of our projects.

        The design, construction and operation of wind energy projects are highly regulated, require various governmental approvals and permits, including environmental approvals and permits, and may be subject to the imposition of related conditions that vary by jurisdiction. In some cases, these approvals and permits require periodic renewal. We cannot predict whether all permits required for a given project will be granted or whether the conditions associated with the permits will be achievable. The denial of a permit essential to a project or the imposition of impractical conditions would impair our ability to develop the project. In addition, we cannot predict whether the permits will attract significant opposition or whether the permitting process will be lengthened due to complexities and appeals. For example, permit challenges delayed the start of construction of our Rollins and Sheffield projects. Delay in the review and permitting process for a project can impair or delay our ability to develop that project or increase the cost so substantially that the project is no longer attractive to us.

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We have experienced delays in developing our projects due to delays in obtaining non-appealable permits and may experience delays in the future. If we were to commence construction in anticipation of obtaining the final, non-appealable permits needed for that project, we would be subject to the risk of being unable to complete the project if all the permits were not obtained. If this were to occur, we would likely lose a significant portion of our investment in the project and could incur a loss as a result. Any failure to procure and maintain necessary permits would adversely affect ongoing development, construction and continuing operation of our projects.

Our development activities and operations are subject to numerous environmental, health and safety laws and regulations.

        We are subject to numerous environmental, health and safety laws and regulations in each of the jurisdictions in which we operate. These laws and regulations require us to obtain and maintain permits and approvals, undergo environmental impact assessments and review processes and implement environmental, health and safety programs and procedures to control risks associated with the siting, construction, operation and decommissioning of wind energy projects. For example, to obtain permits we could be required to undertake expensive programs to protect and maintain local endangered species. If such programs are not successful, we could be subject to penalties or to revocation of our permits. In addition, permits frequently specify permissible sound levels.

        If we do not comply with applicable laws, regulations or permit requirements, we may be required to pay penalties or fines or curtail or cease operations of the affected projects. Violations of environmental and other laws, regulations and permit requirements, including certain violations of laws protecting migratory birds and endangered species, may also result in criminal sanctions or injunctions.

        Environmental, health and safety laws, regulations and permit requirements may change or become more stringent. Any such changes could require us to incur materially higher costs than we currently have. Our costs of complying with current and future environmental, health and safety laws, regulations and permit requirements, and any liabilities, fines or other sanctions resulting from violations of them, could adversely affect our business, financial condition and results of operations.

Our ownership and operation of real property and our disposal of hazardous waste could result in our being liable for environmental issues.

        Certain environmental laws impose liability on current and previous owners and operators of real property for the cost of removal or remediation of hazardous substances. These laws often impose liability even if the owner or operator did not know of, or was not responsible for, the release of such hazardous substances. They can also assess liability on persons who arrange for hazardous substances to be sent to disposal or treatment facilities when such facilities are found to be contaminated. Such persons can be responsible for cleanup costs even if they never owned or operated the contaminated facility. In addition to actions brought by governmental agencies, private plaintiffs may also bring claims arising from the presence of hazardous substances on a property or exposure to such substances. Our liabilities arising from past or future releases of, or exposure to, hazardous substances may adversely affect our business, financial condition and results of operations.

We often rely on transmission lines and other transmission facilities that are owned and operated by third parties. We are exposed to transmission facility development and curtailment risks, which may delay and increase the costs of our projects or reduce the return to us on those investments.

        We often depend on electric transmission lines owned and operated by third parties to deliver the electricity we generate. Some of our projects have limited access to interconnection and transmission capacity because there are many parties seeking access to the limited capacity that is available. We may not be able to secure access to this limited interconnection or transmission capacity at reasonable prices or at all. Moreover, a failure in the operation by third parties of these transmission facilities could

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result in our losing revenues because such a failure could limit the amount of electricity we deliver. In addition, our production of electricity may be curtailed due to third-party transmission limitations or limitations on the grid's ability to accommodate intermittent energy sources, reducing our revenues and impairing our ability to capitalize fully on a particular project's potential. Such a failure or curtailment at levels significantly above which we expect could have a material adverse effect on our business, financial condition and results of operations.

        In certain circumstances, we have developed and in the future will develop our own generator leads from our projects to available electricity transmission or distribution networks when such facilities do not already exist. In some cases, these facilities may cover significant distances. To construct such facilities, we need approvals, permits and land rights, which may be difficult or impossible to acquire or the acquisition of which may require significant expenditures. We may not be successful in these activities, and our projects that rely on such generator lead development may be delayed, have increased costs or not be feasible. Our failure in operating these generator leads could result in lost revenues because it could limit the amount of electricity we are able to deliver. In addition, we may be required by law or regulation to provide service over our facilities to third parties at regulated rates, which could constrain transmission of our power from the affected facilities, or we could be subject to additional regulatory risks associated with being considered the owner of a transmission line.

We may be unable to construct our wind energy projects on time, and our construction costs could increase to levels that make a project too expensive to complete or make the return on our investment in that project less than expected.

        There may be delays or unexpected developments in completing our wind energy projects, which could cause the construction costs of these projects to exceed our expectations. We may suffer significant construction delays or construction cost increases as a result of a variety of factors, including:

•

failure to receive turbines or other critical components and equipment, including batteries, that meet our design specifications and can be delivered on schedule;



•

failure to complete interconnection to transmission networks;



•

failure to obtain all necessary rights to land access and use;



•

failure to receive quality and timely performance of third-party services;



•

failure to secure and maintain environmental and other permits or approvals;



•

appeals of environmental and other permits or approvals that we obtain;



•

failure to obtain capital to develop our pipeline;



•

shortage of skilled labor;



•

inclement weather conditions;



•

adverse environmental and geological conditions; and



•

force majeure or other events out of our control.

        Any of these factors could give rise to construction delays and construction costs in excess of our expectations. This could prevent us from completing construction of a project, cause defaults under our financing agreements or under PPAs that require completion of project construction by a certain time, cause the project to be unprofitable for us, or otherwise impair our business, financial condition and results of operations.

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Demand for wind turbines and related components may increase in the future. In that case, we may face difficulties in obtaining turbines and related components at affordable prices, in a timely manner or in sufficient quantities.

        While the turbine market currently has significant over-capacity, there have been times when the demand for wind turbines and their related components has exceeded supply. Turbine suppliers have at times had difficulty meeting the demand, leading to significant supply backlogs, increased prices, higher up-front payments and deposits and delivery delays. These market conditions may prevail again and if they do, may result in prices that are higher than the costs we expect, less favorable payment terms or may result in insufficient available supplies to sustain our growth. Delays in the delivery of ordered turbines and components could delay the completion of our projects under development.

Warranties from suppliers of turbines, which protect us against turbine non-performance, may be limited by the ability of the vendor to satisfy its obligations under the warranty. In addition, the warranties have time limits and if we are not ready for turbine installation at the time we receive a turbine, that warranty protection can be lost.

        When we purchase turbines, we also enter into warranty agreements with the manufacturer. However, there can be no assurance that the supplier will be able to fulfill its contractual obligations. In addition, these warranties generally expire within two to five years after the turbine delivery date or the date the turbine is commissioned. We may lose all or a portion of the benefit of a warranty if we take delivery of a turbine before we are able to deploy it, as we have in the past. If we seek warranty protection and the vendor is unable or unwilling to perform its obligations under the warranty, whether as a result of the vendor's financial condition or otherwise, or if the term of the warranty has expired, we may suffer reduced warranty availability for the affected turbines, which could have a material adverse effect on our business, financial condition and results of operations. Also, under such warranties, the warranty payments by the manufacturer are typically subject to an aggregate maximum cap that is a portion of the total purchase price of the turbines. Losses in excess of these caps would be our responsibility.

Our use and enjoyment of real property rights for our wind energy projects may be adversely affected by the rights of lienholders and leaseholders that are superior to those of the grantors of those real property rights to us.

        Our wind energy projects generally are and are likely to be located on land we occupy pursuant to long-term easements and leases. The ownership interests in the land subject to these easements and leases may be subject to mortgages securing loans or other liens (such as tax liens) and other easement and lease rights of third parties (such as leases of oil or mineral rights) that were created prior to our easements and leases. As a result, our rights under these easements or leases may be subject, and subordinate, to the rights of those third parties. We perform title searches and obtain title insurance to protect ourselves against these risks. Such measures may, however, be inadequate to protect us against all risk of loss of our rights to use the land on which our projects are located, which could have a material adverse effect on our business, financial condition and results of operations.

Many of our operating projects are, and other future projects may be, subject to regulation by the Federal Energy Regulatory Commission under the Federal Power Act or other regulations that regulate the sale of electricity, which may adversely affect our business.

        Some of our current operating projects are "Qualifying Facilities" (QFs) and/or "Exempt Wholesale Generators" (EWGs) that are exempt from regulation as public utilities by the Federal Energy Regulatory Commission (FERC) under the Federal Power Act (FPA). Many of our operating projects are, however, subject to rate regulation by FERC under the FPA, and certain of our under-construction and development projects may be subject to such rate regulation in the future. Our

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projects that are subject to rate regulation are required to obtain FERC acceptance of their rate schedules for wholesale sales of energy, capacity and ancillary services. FERC may revoke or revise an entity's authorization to make wholesale sales at market-based rates if FERC subsequently determines that such entity can exercise market power in transmission or generation, create barriers to entry or engage in abusive affiliate transactions or market manipulation. In addition, public utilities are subject to FERC reporting requirements that impose administrative burdens and that, if violated, can expose the company to criminal and civil penalties or other risks.

        Any market-based rate authority that we have or will obtain will be subject to certain market behavior rules. If we are deemed to have violated these rules, we will be subject to potential disgorgement of profits associated with the violation and/or suspension or revocation of our market-based rate authority, as well as potential criminal and civil penalties. If we were to lose market-based rate authority for a project, we would be required to obtain FERC's acceptance of a cost-based rate schedule and could become subject to, among other things, the burdensome accounting, record keeping and reporting requirements that are imposed on public utilities with cost-based rate schedules. This could have an adverse effect on the rates we charge for power from our projects and our cost of regulatory compliance.

        For our operating projects with more than 75MW of capacity, we are also subject to the reliability standards of the North American Electric Reliability Corporation (NERC). If we fail to comply with the mandatory reliability standards, we could be subject to sanctions, including substantial monetary penalties.

        Although the sale of electric energy has been to some extent deregulated, the industry is subject to increasing regulation and even possible re-regulation. Due to major regulatory restructuring initiatives at the federal and state levels, the U.S. electric industry has undergone substantial changes over the past several years. We cannot predict the future design of wholesale power markets or the ultimate effect ongoing regulatory changes will have on our business. Other proposals to re-regulate may be made and legislative or other attention to the electric power market restructuring process may delay or reverse the movement towards competitive markets. If deregulation of the electric power markets is reversed, discontinued or delayed, our business, financial condition and results of operations could be adversely affected.

Current or future litigation or administrative proceedings could have a material adverse effect on our business, financial condition and results of operations.

        We have been and continue to be involved in legal proceedings, administrative proceedings, claims and other litigation that arise in the ordinary course of business. Individuals and interest groups may sue to challenge the issuance of a permit for a wind energy project or seek to enjoin construction of a wind energy project. For example, proceedings have been instituted against us challenging the issuance of some of our permits. In addition, we may be subject to legal proceedings or claims contesting the construction or operation of our wind energy projects. For example, some residents near our Mars Hill project have commenced litigation against us based on our construction and operation of the project, including complaints relating to sound levels. Unfavorable outcomes or developments relating to these proceedings, such as judgments for monetary damages, injunctions or denial or revocation of permits, could have a material adverse effect on our business, financial condition and results of operations. In addition, settlement of claims could adversely affect our financial condition and results of operations. See "Business—Legal Proceedings."

Acquisition of existing wind energy assets involves numerous risks.

        Our strategy includes acquiring wind energy assets at various stages of development. The acquisition of existing wind energy assets involves numerous risks. They include: difficulty in developing the assets into operating projects; unanticipated costs and exposure to liabilities; difficulty in integrating

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the acquired assets; and, if the assets are in new markets, the risks of entering markets where we have limited experience. A failure to achieve the financial returns we expect when we acquire wind energy assets could have an adverse effect on our business.

We are not able to insure against all potential risks and may become subject to higher insurance premiums.

        Our business is exposed to the risks inherent in the construction and operation of wind energy projects, such as breakdowns, manufacturing defects, natural disasters, terrorist attacks and sabotage. We are also exposed to environmental risks. We have insurance policies covering certain risks associated with our business. Our insurance policies do not, however, cover losses as a result of force majeure, natural disasters, terrorist attacks or sabotage, among other things. We generally do not maintain insurance for certain environmental risks, such as environmental contamination. In addition, our insurance policies are subject to annual review by our insurers and may not be renewed at all or on similar or favorable terms. A serious uninsured loss or a loss significantly exceeding the limits of our insurance policies could have a material adverse effect on our business, financial condition and results of operations.

The loss of one or more members of our senior management or key employees may adversely affect our ability to implement our strategy.

        We depend on our experienced management team and the loss of one or more key executives could have a negative impact on our business. We also depend on our ability to retain and motivate key employees and attract qualified new employees. Because the wind industry is relatively new, there is a scarcity of top-quality employees with experience in the wind industry. If we lose a member of the management team or a key employee, we may not be able to replace him or her. Integrating new employees into our management team and training new employees with no prior experience in the wind industry could prove disruptive to our operations, require a disproportionate amount of resources and management attention and ultimately prove unsuccessful. An inability to attract and retain sufficient technical and managerial personnel could limit or delay our development efforts, which could have a material adverse effect on our business, financial condition and results of operations.

Risks Related to Our Financial Activities

We may not be able to finance the growth of our business, including the development and construction of our wind energy projects and the growth of our organization.

        We are in a capital intensive business and rely heavily on the debt and equity markets to finance the development and construction costs of our projects and other projected capital expenditures. Completion of our projects requires significant capital expenditures and construction costs. Recovery of the capital investment in a wind energy project generally occurs over a long period of time. As a result, we must obtain funds from equity or debt financings, including tax equity transactions, or from government grants to develop and construct our existing project pipeline, to finance the acquisition of turbines, to identify and develop new projects and to pay the general and administrative costs of operating our business. The cost of turbines has historically represented approximately 70% of the total cost of an average wind energy project. The significant disruption in credit and capital markets generally that began in the fall of 2008 and has persisted has made it difficult to obtain financing on acceptable terms or, in some cases, at all. If we are unable to raise additional funds when needed, we could delay development and construction of projects, reduce the scope of projects or abandon or sell some or all of our development projects, or default on our contractual commitments to buy turbines in the future, any of which would adversely affect our business, financial condition and results of operations.

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Our substantial amount of indebtedness maturing in less than one year may adversely affect our ability to operate our business, remain in compliance with debt covenants and make payments on our indebtedness.

        As of September 30, 2010, we had outstanding indebtedness of approximately $582.2 million, which represented approximately 36.1% of our total debt and equity capitalization of $1,610.6 million (after giving effect to this offering and giving effect to the pro forma as adjusted assumptions set forth under "Capitalization"), including:

•

$161.4 million of debt under turbine supply loans;



•

$362.0 million of holding company and project term debt; and



•

$58.8 million of other debt used to fund development, construction and general and administrative expenses.

        Of this amount, approximately $112.0 million matures prior to October 1, 2011. We do not have available cash or short-term liquid investments sufficient to repay all of this indebtedness and we have not obtained commitments for refinancing all of this debt. Therefore, we may not be able to extend the maturity of this indebtedness or to otherwise successfully refinance current maturities. If we are unable to repay or further extend the maturity on the $94.1 million of turbine supply loans ($161.4 million total at September 30, 2010, less $67.3 million repaid with proceeds from the Milford II construction loan, which closed on October 20, 2010) included in this current indebtedness, we would be in default on these loans. In that event, we may be forced to sell the collateral securing the loans or surrender the collateral to the lender, which would result in a loss for financial reporting purposes and could have an adverse effect on our longer term operations, including a potential delay in completion of one or more of our Tier 1 projects.

        The initial report of our independent registered public accounting firm, dated April 30, 2009, on our consolidated financial statements as of and for the year ended December 31, 2008, contained an explanatory paragraph regarding our ability to continue as a going concern. After April 30, 2009, we obtained additional funding that removed the substantial doubt about whether we would continue as a going concern through December 31, 2009. The report of our independent registered public accounting firm dated March 24, 2010, on our consolidated financial statements as of and for the year ended December 31, 2009, does not contain such an explanatory paragraph; however, there may be in the future circumstances that raise substantial doubt about our ability to continue as a going concern. If doubts about our ability to continue as a going concern are raised in the future notwithstanding the additional funding we have obtained and the funding we will obtain from this offering, our stock price could drop and our ability to raise additional funds, to obtain credit on commercially reasonable terms or to remain in compliance with our covenants with lenders may be adversely affected.

        In addition, the assets of some of our subsidiaries collateralize their indebtedness, and in certain cases the assets of certain subsidiaries collateralize the indebtedness of other subsidiaries. This cross-collateralization means that a default by one subsidiary could trigger adverse consequences for other subsidiaries, including possible defaults under their debt agreements, which could have a material adverse effect on our business, financial condition and results of operations.

        Our substantial indebtedness could have important consequences. For example, it could:

•

make it difficult for us to satisfy our obligations with respect to our indebtedness, and failure to comply with these obligations could result in an event of default under those agreements, which could be difficult to cure, or result in our bankruptcy;



•

require us to dedicate an even greater portion of our cash flow to pay principal and interest on our debt, reducing the funds available to us and our ability to borrow to operate and grow our business;



•

limit our flexibility to plan for and react to unexpected opportunities;

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•

make us vulnerable to adverse changes in general economic, credit and capital markets, industry and competitive conditions and adverse changes in government regulation; and



•

place us at a disadvantage compared with competitors with less debt.

        Any of these consequences could materially and adversely affect our business, financial condition and results of operations. If we do not comply with our obligations under our debt instruments, we may be required to refinance all or part of our existing debt, borrow additional amounts or sell securities, which we may not be able to do on favorable terms, or at all. In addition, increases in interest rates and changes in debt covenants may reduce the amounts that we can borrow, reduce our net cash flow and increase the equity investment we may be required to make to complete development and construction of our projects. These increases could cause some of our projects to become economically unattractive. If we are unable to raise additional capital or generate sufficient operating cash flow to repay our indebtedness, we could be in default under our lending agreements and could be required to delay development and construction of our wind energy projects, reduce overhead costs, reduce the scope of our projects or abandon or sell some or all of our development projects, all of which could have a material adverse effect on our business, financial condition and results of operations.

If our subsidiaries default on their obligations under their debt instruments, we may need to make payments to lenders to prevent foreclosure on the collateral securing the debt, which would cause us to lose certain of our wind energy projects.

        Our subsidiaries incur various types of debt. Non-recourse debt is repayable solely from the applicable project's revenues and is secured by the project's physical assets, major contracts, cash accounts and, in many cases, our ownership interest in the project subsidiary. Limited recourse debt is debt where we have provided a limited guarantee and recourse debt is debt where we have provided a full guarantee, which means if our subsidiaries default on these obligations, we will be liable directly to those creditors, although in the case of limited recourse debt only to the extent of our limited recourse obligations. To satisfy these obligations, we may be required to use amounts distributed by our other subsidiaries as well as other sources of available cash, reducing the cash available to execute our business plan. In addition, if our subsidiaries default on their obligations under non-recourse financing agreements, we may decide to make payments to prevent the creditors of these subsidiaries from foreclosing on the relevant collateral. Such a foreclosure would result in our losing our ownership interest in the subsidiary or in some or all of its assets. The loss of our ownership interest in one or more of our subsidiaries or some or all of their assets could have a material adverse effect on our business, financial condition and results of operations.

Our hedging activities may not adequately manage our exposure to commodity and financial risk, may result in significant losses or require us to use cash collateral to meet margin requirements, each of which could adversely affect our results of operations and cash flow. Liquidity constraints could impair our ability to execute favorable financial hedges in the future.

        Our ownership and operation of wind energy projects exposes us to volatility in market prices of electricity and RECs.

        In an effort to stabilize our revenue from electricity sales, we evaluate the electricity sale options for each of our development projects, including the appropriateness of entering into a PPA or a financial swap, or both. If we sell our electricity into an independent system operator (ISO) market without a PPA, we may enter into a financial swap to stabilize all or a portion of our estimated revenue stream. Under the terms of our existing financial swaps, we are not obligated to physically deliver or purchase electricity. Instead, we receive payments for specified quantities of electricity based on a fixed price and are obligated to pay our counterparty the market price for the same quantities of electricity. These financial swaps cover quantities of electricity that we estimate we are highly likely to produce. As a result, gains or losses under the financial swaps are designed to be offset by decreases or increases in

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our revenues from spot sales of electricity in liquid ISO markets. However, the actual amount of electricity we generate from operations may be materially different from our estimates for a variety of reasons, including variable wind conditions and turbine availability. If a project does not generate the volume of electricity covered by the associated swap contract, we could incur significant losses if electricity prices in the market rise substantially above the fixed price provided for in the swap. If a project generates more electricity than is contracted in the swap, the excess production will not be hedged and the revenues we derive will be exposed to market price fluctuations.

        We would also incur financial losses as a result of adverse changes in the mark-to-market values of the financial swaps or if the counterparty fails to make payments. We could also experience a reduction in operating cash flow if we are required to post margin in the form of cash collateral. We often are required to post cash collateral and issue letters of credit, which fluctuate based on changes in commodity prices, to backstop our obligations under our hedging arrangements. These actions reduce our available borrowing capacity under the credit facilities under which these letters of credit are issued. We have been and expect in the future to be required to post additional cash collateral or issue additional letters of credit if electricity and oil prices rise. We may be exposed to counterparty credit risk, and may suffer losses, if we enter into hedges with entities that are not creditworthy or we obtain credit support that is inadequate with respect to a counterparty.

        We enter into PPAs when we sell our electricity into non-ISO markets or where we believe it is otherwise advisable. Under a PPA, we contract to sell all or a fixed proportion of the electricity generated by one of our projects, sometimes bundled with RECs and capacity, to a customer, often a utility. We do this to stabilize our revenues from that project. We are exposed to the risk that the customer will fail to perform under a PPA, with the result that we will have to sell our electricity at the market price, which could be disadvantageous in the case of fixed-price PPAs. We also in some instances commit to sell minimum levels of generation. If the project generates less than the committed volumes, we may be required to buy the shortfall of electricity on the open market or make payments of liquidated damages.

        We often seek to sell forward a portion of our RECs to fix the revenues from those attributes and hedge against future declines in prices of RECs. If our projects do not generate the amount of electricity required to earn the RECs sold forward or if for any reason the electricity we generate does not produce RECs for a particular state we may be required to make up the shortfall of RECs through purchases on the open market or make payments of liquidated damages. Further, current market conditions may limit our ability to hedge sufficient volumes of our anticipated RECs, leaving us exposed to the risk of falling prices for RECs. Future prices for RECs are also subject to the risk that regulatory changes will adversely affect prices.

We are subject to credit and performance risk from third parties under service and supply contracts.

        We enter into contracts with vendors to supply equipment, materials and other goods and services for the development, construction and operation of wind projects as well as for other business operations. If vendors do not perform their obligations, we may have to enter into new contracts with other vendors at a higher cost or may have schedule disruptions.

We rely on tax equity financing arrangements to realize the benefits provided by PTCs and accelerated tax depreciation. These arrangements may limit the cash distributions we receive and restrict the manner in which we conduct our business.

        Through September 30, 2010, we have entered into four tax equity financing transactions in which we received an aggregate of $388 million ($146.3 million in two transactions in 2007, $19.7 million in 2008 and $222.1 million in 2009) from tax equity investors in return for investments in our projects. The 2009 amount of $222.1 million consisted of an equity investment of $102.1 million and a redeemable interest of $120 million. We repaid the redeemable interest in March 2010 with the

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proceeds from an ARRA cash grant. The tax equity investors are entitled to most of the applicable project's operating cash flow from electricity sales and related hedging activities, and substantially all of the PTCs and taxable income or loss until they achieve their respective agreed rates of return, which we expect to occur in 10 years.

        As a result, a tax equity financing substantially reduces the cash distributions from the applicable project available to us for other uses, and the period during which the tax equity investors receive most of the cash distributions from electricity sales and related hedging activities may last longer than expected if our wind energy projects perform below our expectations.

        Our ability to enter into tax equity arrangements in the future depends on the extension of the expiration date or renewal of the PTC, without which the market for tax equity financing would likely cease to exist. Moreover, there are a limited number of potential tax equity investors, they have limited funds and wind energy developers compete with other renewable energy developers and others for tax equity financing. In addition, conditions in financial and credit markets generally may result in the contraction of available tax equity financing. As the renewable energy industry expands, the cost of tax equity financing may increase and there may not be sufficient tax equity financing available to meet the total demand in any year. If we are unable to enter into tax equity financing agreements with attractive pricing terms or at all, we may not be able to use the tax benefits provided by PTCs and accelerated tax depreciation, which could have a material adverse effect on our business, financial condition and results of operations.

        Our tax equity financing agreements provide our tax equity investors with various approval rights with respect to the applicable project or projects, including approvals of annual budgets, indebtedness, incurrence of liens, sales of assets outside the ordinary course of business and litigation settlements. These approval rights may restrict how we conduct our business.

We have had material weaknesses and significant deficiencies in our internal control over financial reporting. Any material weaknesses or significant deficiencies in our internal controls could result in a material misstatement in our financial statements as well as result in our inability to file periodic reports timely as required by federal securities laws, which could have a material adverse effect on our business and stock price.

        We are required to design, implement and maintain effective controls over financial reporting. A material weakness is a deficiency, or a combination of deficiencies, in internal control over financial reporting such that there is a reasonable possibility that a material misstatement of a company's annual or interim financial statements will not be prevented or detected on a timely basis.

        We have had material weaknesses in our internal control over financial reporting that related to the adequacy of our financial and accounting organization support for our financial accounting and reporting needs. These weaknesses mainly resulted from a lack of sufficient personnel, and contributed to significant deficiencies related to: (1) effective policies and procedures designed to ensure certain costs are capitalized in accordance with generally accepted accounting principles and captured in the appropriate accounting period; (2) an effective process to ensure the completeness of accounts payable and accrued expenses; and (3) an effective review, approval and communications process for journal entries.

        While we are implementing procedures designed to remediate these weaknesses and deficiencies, we cannot be certain that we will not in the future have material weaknesses or significant deficiencies in our internal control over financial reporting, or that we will successfully remediate any that we find. If, in the future, we have weaknesses or deficiencies in our internal controls, that could result in a material misstatement in our annual or interim consolidated financial statements or cause us to fail to meet our obligations to file periodic financial reports with the SEC. We also may not be able conclude on an ongoing basis that we have effective internal control over financial reporting as contemplated by Section 404 of the Sarbanes-Oxley Act of 2002 or our independent registered public accounting firm

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may issue an adverse opinion on the effectiveness of our internal control over financial reporting. Any of these failures could result in adverse consequences that could materially and adversely affect our business, including potential action by the SEC against us, possible defaults under our debt agreements, stockholder lawsuits, delisting of our stock and general damage to our reputation.

Risks Related to Our Structure

We are a holding company and our only material asset after completion of the reorganization and this offering will be our interest in First Wind Holdings, LLC, and accordingly we are dependent upon distributions from First Wind Holdings, LLC to pay taxes and other expenses.

        We will be a holding company and will have no material assets other than our ownership of Series A Membership Interests of First Wind Holdings, LLC. We will have no independent means of generating revenue. First Wind Holdings, LLC will be treated as a partnership for U.S. federal income tax purposes and, as such, will not itself be subject to U.S. federal income tax. Instead, its taxable income will generally be allocated to its members, including us, pro rata according to the number of membership units each member owns. Accordingly, we will incur income taxes on our proportionate share of any net taxable income of First Wind Holdings, LLC and also will incur expenses related to our operations. We intend to cause First Wind Holdings, LLC to distribute cash to its members in an amount at least equal to the amount necessary to cover their tax liabilities, if any, with respect to their allocable share of the net income of First Wind Holdings, LLC. To the extent that we need funds to pay our tax or other liabilities or to fund our operations, and First Wind Holdings, LLC is restricted from making distributions to us under applicable agreements, laws or regulations or does not have sufficient cash to make these distributions, we may have to borrow funds to meet these obligations and operate our business and our liquidity and financial condition could be materially adversely affected.

We will be required to pay certain holders of Series B Membership Interests most of the tax benefit of any depreciation or amortization deductions we may claim as a result of the tax basis step up we receive in connection with future exchanges of Series B Membership Interests.

        We expect that any future exchanges of Series B Membership Interests (together with an equal number of shares of our Class B common stock) for shares of our Class A common stock will result in increases in the tax basis in the tangible and intangible assets of First Wind Holdings, LLC. Any such increases in tax basis would reduce the amount of tax that we would otherwise be required to pay in the future. We will be required to pay a portion of the cash savings we actually realize from such increase to certain holders of the Series B Membership Interests, which include our Sponsors and certain of our employees and current investors, pursuant to a tax receivable agreement. See "The Reorganization and Our Holding Company Structure—Tax Receivable Agreement."

        We intend to enter into a tax receivable agreement with certain current members of First Wind Holdings, LLC and certain future holders of the Series B Membership Interests, pursuant to which we will pay them 85% of the amount of the cash savings, if any, in U.S. federal, state and local income tax that we realize (or are deemed to realize in the case of an early termination payment by us, or a change in control, as discussed below) as a result of these possible future increases in tax basis. Any actual increases in tax basis, as well as the amount and timing of any payments under the tax receivable agreement cannot be predicted reliably at this time. The amount of any such increases will vary depending upon a number of factors, including the timing of exchanges, the price of our Class A common stock at the time of the exchanges, the extent to which such exchanges are taxable, the amount and timing of our income and the tax rates then applicable. As a result of the size and increases in our share of the tax basis in the tangible and intangible assets of First Wind Holdings, LLC attributable to our interest therein, the payments that we may be required to make pursuant to the tax receivable agreement could be substantial for periods in which we generate taxable income. However, because we have not generated taxable income to date and do not expect to generate taxable income in

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the near-term, it is difficult to predict when and if we will make payments under the tax receivable agreement. Assuming no material changes in the relevant tax law and based on our current operating plan and other assumptions, including our estimate of the tax basis of our assets as of December 31, 2009, if all of the Series B Membership Interests were acquired by us in taxable transactions at the time of the closing of this offering for a price of $25.00 (the midpoint of the range on the cover of this prospectus) per Series B Membership Interest, we estimate that the amount that we would be required to pay under the tax receivable agreement could be approximately $45.0 million. The actual amount may materially differ from this hypothetical amount, as potential future payments will be calculated using the market value of our Class A shares and the prevailing tax rates at the time of relevant exchange and will be dependent on us generating sufficient future taxable income to realize the benefit.

        If the Internal Revenue Service successfully challenges the tax basis increases described above, we will not be reimbursed for any payments made under the tax receivable agreement. As a result, in certain circumstances, we could be required to make payments under the tax receivable agreement in excess of our cash tax savings.

If we are deemed to be an investment company under the Investment Company Act, our business would be subject to applicable restrictions under that Act, which could make it impracticable for us to continue our business as contemplated.

        We believe our company is not an investment company under the Investment Company Act because we are the managing member of First Wind Holdings, LLC and we are primarily engaged in a non-investment company business. We intend to conduct our operations so that we will not be an investment company. However, if we are deemed an investment company, restrictions imposed by the Investment Company Act, including limitations on our capital structure and our ability to transact with affiliates, and changes in financial reporting and regulatory disclosure requirements as a result of being an investment company, could make it impractical for us to continue operating our business as contemplated.

Risks Related to this Offering and Our Class A Common Stock

We will continue to be controlled by our Sponsors after the completion of this offering, which will limit your ability to influence corporate activities and may adversely affect the market price of our Class A common stock.

        Upon completion of the offering, the D. E. Shaw group and Madison Dearborn will own or control outstanding common stock representing, in the aggregate, an approximately 70.6% voting interest in us, or approximately 68.1%, if the underwriters exercise their over-allotment option in full. As a result of this ownership, our Sponsors will have effective control over the outcome of votes on all matters requiring approval by our stockholders, including the election of directors, the adoption of amendments to our certificate of incorporation and bylaws and approval of a sale of the company and other significant corporate transactions. Our Sponsors can also take actions that have the effect of delaying or preventing a change in control of us or discouraging others from making tender offers for our shares, which could prevent stockholders from receiving a premium for their shares. These actions may be taken even if other stockholders oppose them. Prior to the completion of this offering we and our Sponsors will enter into a nominating and voting agreement pursuant to which we will agree to nominate individuals designated by our Sponsors to the board of directors and the Sponsors will agree to vote all of the shares of Class A common stock and Class B common stock held by them together on certain matters submitted to a vote of our common stockholders, as described under "The Reorganization and Our Holding Company Structure—Nominating and Voting Agreement."

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The interests of our Sponsors may conflict with the interests of our other stockholders.

        The interests of our Sponsors, or entities controlled by them, may not coincide with the interests of the holders of our Class A common stock. For example, our Sponsors could cause us to make acquisitions or engage in other transactions that increase the amount of our indebtedness or the number of outstanding shares of Class A common stock or sell revenue-generating assets. Additionally, our Sponsors are in the business of trading securities of, and/or investing in, energy companies, including wind energy producers, and related products, including derivatives, commodities and power, and may, from time to time, compete directly or indirectly with us or prevent us from taking advantage of corporate opportunities. Our Sponsors may also pursue acquisition opportunities that may be complementary to our business, and as a result, those acquisition opportunities may not be available to us.

Conflicts of interest may arise because some of our directors are representatives of our controlling stockholders.

        Messrs. Aube, Eilers, Martin and Raino, who are representatives of our Sponsors, serve on our board of directors. As discussed above, our Sponsors and entities controlled by them may hold equity interests in entities that directly or indirectly compete with us, and companies in which they currently invest may begin competing with us. As a result of these relationships, when conflicts between the interests of our Sponsors, on the one hand, and the interests of our other stockholders, on the other hand, arise, these directors may not be disinterested. Although our directors and officers have a duty of loyalty to us under Delaware law and our certificate of incorporation, transactions that we enter into in which a director or officer has a conflict of interest are generally permissible so long as (1) the material facts relating to the director's or officer's relationship or interest as to the transaction are disclosed to our board of directors and a majority of our disinterested directors, or a committee consisting solely of disinterested directors, approves the transaction, (2) the material facts relating to the director's or officer's relationship or interest as to the transaction are disclosed to our stockholders and a majority of our disinterested stockholders approves the transaction or (3) the transaction is otherwise fair to us. Under our certificate of incorporation, representatives of our Sponsors are not required to offer to us any transaction opportunity of which they become aware and could take any such opportunity for themselves or offer it to other companies in which they have an investment, unless such opportunity is offered to them solely in their capacity as a director of ours.

We have limited the liability of, and have agreed to indemnify, our Sponsors, their affiliates and their subsidiaries, as well as our directors and officers, which may result in these parties assuming greater risks.

        The liability of our Sponsors, their affiliates and their subsidiaries, as well as of our directors and officers, is limited, and we have agreed to indemnify each of these parties to the fullest extent permitted by law. This may lead such parties to assume greater risks when making investment-related decisions than they otherwise would.

        Under our certificate of incorporation and bylaws, the liability of our directors, officers and employees is limited. Similarly, First Wind Holdings, LLC's limited liability company agreement contains provisions limiting its managing member's, members', officers' and their respective affiliates', including our Sponsors', liability to First Wind Holdings, LLC and its unit holders. Because First Wind Holdings, LLC is a limited liability company, the exculpation and indemnification provisions in its limited liability company agreement are not subject to the limitations set forth in the Delaware General Corporation Law with respect to the indemnification that may be provided by a Delaware corporation to its directors and officers. In addition, we have contractually agreed to indemnify our directors to the fullest extent permitted by law. These protections may result in the indemnified parties' tolerating greater risks when making investment-related decisions than otherwise would be the case, for example when determining whether to use leverage in connection with investments. The indemnification

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arrangements may also give rise to legal claims for indemnification that are adverse to us and holders of our common stock.

We will be a "controlled company" within the meaning of Nasdaq Listing Rules and, as a result, will qualify for, and rely on, applicable exemptions from certain corporate governance requirements.

        After completion of this offering we will be a "controlled company" under the listing rules of the Nasdaq Stock Market (Nasdaq Listing Rules). Under these rules, a company of which more than 50% of the voting power is held by a group is a "controlled company" and may elect not to comply with certain corporate governance requirements under the Nasdaq Listing Rules, including (1) the requirement that a majority of the board of directors consist of independent directors, (2) the requirement that the nominating committee be composed entirely of independent directors, (3) the requirement that the compensation committee be composed entirely of independent directors and (4) the requirement for an annual performance evaluation of the nominating and corporate governance and compensation committees. We intend to rely on this exemption to the extent it is applicable, and therefore we will not have a majority of independent directors or nominating and compensation committees consisting entirely of independent directors. Accordingly, you will not have the same protections afforded to stockholders of companies that are not deemed "controlled companies."

The market price of our Class A common stock could decline due to the large number of shares of Class A common stock eligible for future sale upon the exchange of Series B Membership Interests.

        The market price of our Class A common stock could decline as a result of sales of a large number of shares of our Class A common stock eligible for future sale upon the exchange of Series B Membership Interests (together with an equal number of shares of our Class B common stock), or the perception that such sales could occur. These sales, or the possibility that these sales may occur, also may make it more difficult for us to raise additional capital by selling equity securities in the future, at a time and price that we deem appropriate.

        After completion of this offering, approximately 23,239,140 Series B Membership Interests of First Wind Holdings, LLC will be outstanding. Each Series B Membership Interest, together with a share of Class B common stock, will be exchangeable for one share of Class A common stock as described under "The Reorganization and Our Holding Company Structure—Limited Liability Company Agreement of First Wind Holdings, LLC." We will enter into a registration rights agreement with our current investors pursuant to which we will grant such investors registration rights with respect to shares of Class A common stock.

Requirements associated with being a public company will increase our costs significantly, as well as divert significant company resources and management attention.

        Before this offering, we have not been subject to the reporting requirements of the Exchange Act or the other rules and regulations of the SEC or any stock exchange relating to publicly-held companies. We are working with our legal, independent auditing and financial advisors to identify those areas in which changes should be made to our financial and management control systems to manage our growth and fulfill our obligations as a public company. These areas include corporate governance, corporate controls, internal audit, disclosure controls and procedures, financial reporting and accounting systems. We have made, and will continue to make, changes in these and other areas. However, the expenses that will be required in order to prepare adequately for being a public company could be material. Compliance with the various reporting and other requirements applicable to public companies will also require considerable management time and attention.

        In addition, being a public company could make it more difficult or more costly for us to obtain certain types of insurance, including directors' and officers' liability insurance, and we may be forced to

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accept reduced policy limits and coverage or incur substantially higher costs to obtain the same or similar coverage.

Our certificate of incorporation, bylaws and Delaware law contain provisions that could discourage another company from acquiring us, may prevent attempts by our stockholders to replace or remove our current management and could negatively affect our stock price.

        Some provisions of our certificate of incorporation, bylaws and Delaware law may have the effect of delaying, discouraging or preventing a merger or acquisition that our stockholders may consider favorable, including transactions in which stockholders may receive a premium for their shares. In addition, these provisions may frustrate or prevent any attempts by our stockholders to replace or remove our current management by making it more difficult for stockholders to replace or remove our board of directors. Our certificate of incorporation and bylaws:

•

authorize the issuance of "blank check" preferred stock that could be issued by our board of directors to thwart a takeover attempt without further stockholder approval;



•

prohibit cumulative voting in the election of directors, which would otherwise allow holders of less than a majority of stock to elect some directors;



•

require super majority (66²/3%) voting to effect amendments to provisions of our certificate of incorporation or bylaws regarding board composition, renouncement of business opportunities and other amendments to our certificate of incorporation or bylaws described above;



•

state that as long as the Class A common stock and the Class B common stock held by our Sponsors and their affiliates, portfolio companies and designated members of our board of directors constitutes more than 50% of the total voting power of all of our capital stock, any action required or permitted to be taken at any annual or special meeting of stockholders may be taken by written consent of stockholders without a meeting; and



•

state that only our board of directors, the Chairman of the board of directors, our Chief Executive Officer and, if the Class A common stock and the Class B common stock held by our Sponsors and their affiliates, portfolio companies and designated members of our board of directors constitutes more than 50% of our total voting power, holders of such Class A common stock and Class B common stock (treated as a single class), are permitted to call a special meeting of stockholders.

        Upon completion of this offering at an assumed initial public offering price of $25.00 per share (the midpoint of the range set forth on the cover of this prospectus), assuming no exercise of the underwriters' over-allotment option, our Class B common stockholders will own 48.4% of our total voting power.

        These provisions could limit the price that investors are willing to pay in the future for shares of our Class A common stock. These provisions may also discourage a potential acquisition proposal or tender offer, even if the acquisition proposal or tender offer is at a premium over the then-current market price for our Class A common stock.

Our Class A common stock has not traded publicly before this offering, and we expect the price of our Class A common stock to fluctuate substantially.

        There has not been a public market for our Class A common stock before this offering. A trading market for our Class A common stock may not develop or be liquid. If you purchase shares of our Class A common stock in this offering, you will pay a price that was not established in the public trading markets. The initial public offering price was determined by negotiations between the underwriters and us. You may not be able to resell your shares above the initial public offering price and may suffer a loss of some or all of your investment.

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        Broad market and industry factors may adversely affect the market price of our Class A common stock, regardless of our actual operating performance. Other factors that could cause fluctuations in our stock price may include, among other things, the numerous risks and uncertainties as described under "Risk Factors" and under "Cautionary Statement Regarding Forward-Looking Statements."

Factors over which we have little or no control may cause our operating results to vary widely from period to period, which may cause our stock price to decline.

        Our operating results may fluctuate from period to period depending on several factors, including varying weather conditions; changes in regulated or market electricity prices; electricity demand, which follows broad seasonal demand patterns; changes in market prices for RECs; marking to market of our hedging arrangements; and unanticipated development or construction delays. Thus, a period-to-period comparison of our operating results may not reflect long-term trends in our business and may not prove to be a relevant indicator of future earnings. These factors may harm our business, financial condition and results of operations and may cause our stock price to decline.

We currently do not intend to pay dividends on our Class A common stock. As a result, your only opportunity to achieve a return on your investment is if the price of our Class A common stock appreciates.

        We currently do not expect to declare or pay dividends on our Class A common stock. Our debt agreements currently limit our ability to pay dividends on our Class A common stock, and we may also enter into other agreements in the future that prohibit or restrict our ability to declare or pay dividends on our Class A common stock. As a result, your only opportunity to achieve a return on your investment will be if the market price of our Class A common stock appreciates and you sell your shares at a profit.

You may experience dilution of your ownership interest due to the future issuance of additional shares of our Class A common stock.

        We are in a capital intensive business and we do not have sufficient funds to finance the growth of our business or the construction costs of our development projects or to support our projected capital expenditures. As a result, we will require additional funds from further equity or debt financings, including tax equity financing transactions or sales of preferred shares or convertible debt to complete the development of new projects and pay the general and administrative costs of our business. We may in the future issue our previously authorized and unissued securities, resulting in the dilution of the ownership interests of purchasers of Class A common stock offered hereby. We are currently authorized to issue 325,000,000 shares of common stock and 5,000,000 shares of preferred stock with preferences and rights as determined by our board of directors. The potential issuance of such additional shares of common stock or preferred stock or convertible debt may create downward pressure on the trading price of our Class A common stock. We may also issue additional shares of Class A common stock or other securities that are convertible into or exercisable for Class A common stock in future public offerings or private placements for capital raising purposes or for other business purposes, potentially at an offering price or conversion price that is below the offering price for Class A common stock in this offering.

You will suffer immediate and substantial dilution in the book value per share of your Class A common stock as a result of this offering.

        The initial public offering price of our Class A common stock is considerably more than the pro forma net tangible book value per share of our outstanding Class A common stock, as adjusted to reflect completion of this offering. This reduction in the book value of your equity is known as dilution. This dilution occurs in large part because our earlier investors paid substantially less than the initial public offering price when they purchased their shares. Investors purchasing Class A common stock in this offering will incur immediate dilution of $2.75 in pro forma net tangible book value per share of Class A common stock, as adjusted to reflect completion of this offering and giving effect to the pro forma as adjusted assumptions set forth under "Capitalization."

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CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

        Various statements in this prospectus, including those that express a belief, expectation or intention, as well as those that are not statements of historical fact, are forward-looking statements. The forward-looking statements may include projections and estimates concerning the timing and success of specific projects, revenues, income and capital spending. We generally identify forward-looking statements with the words "believe," "intend," "expect," "seek," "may," "should," "anticipate," "could," "estimate," "plan," "predict," "project" or their negatives, and other similar expressions. All statements we make relating to our estimated and projected earnings, margins, costs, expenditures, cash flows, growth rates and financial results or to our expectations regarding future industry trends are forward-looking statements.

        These forward-looking statements are subject to risks and uncertainties that may change at any time, and, therefore, our actual results may differ materially from those that we expected. The forward-looking statements contained in this prospectus are largely based on our expectations, which reflect many estimates and assumptions made by our management. These estimates and assumptions reflect our best judgment based on currently known market conditions and other factors. Although we believe such estimates and assumptions are reasonable, we caution that it is very difficult to predict the impact of known factors and it is impossible for us to anticipate all factors that could affect our actual results. In addition, management's assumptions about future events may prove to be inaccurate. We caution all readers that the forward-looking statements contained in this prospectus are not guarantees of future performance, and we cannot assure any reader that such statements will prove correct or the forward-looking events and circumstances will occur. Actual results may differ materially from those anticipated or implied in the forward-looking statements due to the numerous risks and uncertainties as described under "Risk Factors" and elsewhere in this prospectus. All forward-looking statements are based upon information available to us on the date of this prospectus. We undertake no obligation to update or revise any forward-looking statements as a result of new information, future events or otherwise, except as otherwise required by law. These cautionary statements qualify all forward-looking statements attributable to us, or persons acting on our behalf. The risks, contingencies and uncertainties associated with our forward-looking statements relate to, among other matters, the following:

•

our ability to complete our wind energy projects or acquire wind energy assets;



•

fluctuations in supply, demand, prices and other conditions for electricity, other commodities and RECs;



•

changes in law;



•

public response to and changes in the local, state and federal regulatory framework affecting renewable energy projects, including the potential expiration or extension of the PTC, ITC and the related U.S. Treasury grants and potential reductions in RPS requirements;



•

the ability of our counterparties to satisfy their financial commitments;



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the availability of financing, including tax equity financing, for our wind energy projects;



•

our ability to continue as a going concern;



•

risks associated with our hedging strategies;



•

our substantial short-term and long-term indebtedness;



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competition from other energy developers;



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development constraints, including limited geographic availability for suitable sites, obtaining permits on a timely basis and availability of interconnection;

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•

the limited operating history of and technical issues experienced by one of our key turbine suppliers, Clipper;



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potential environmental liabilities and the cost of compliance with applicable environmental laws and regulations;



•

our electrical production projections (including assumptions of curtailment and facility availability) for our wind energy projects;



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our ability to operate our business efficiently, manage capital expenditures and costs (including general and administrative expenses) effectively and generate cash flow;



•

our ability to retain and attract senior management and key employees;



•

our ability to keep pace with and take advantage of new technologies;



•

availability of suitable wind resources and other weather conditions that affect our electricity production;



•

the effects of litigation, including administrative and other proceedings or investigations relating to our wind energy projects under development and those in operation;



•

conditions in energy markets as well as financial markets generally, which will be affected by interest rates, foreign currency fluctuations and general economic conditions;



•

strains on our resources due to the expansion of our business;



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non-payment by customers and enforcement of certain contractual provisions;



•

the effective life and cost of maintenance of our wind turbines and other equipment; and



•

other factors discussed under "Risk Factors."

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MARKET AND INDUSTRY DATA

        This prospectus includes market and industry data that we have developed from independent consultant reports, publicly available information, various industry publications, other published industry sources and our internal data and estimates. Our internal data, estimates and forecasts are based upon information obtained from trade and business organizations and other contacts in the markets in which we operate and our management's understanding of industry conditions.

USE OF PROCEEDS

        We estimate that the net proceeds to us from the sale of Class A common stock in this offering will be approximately $275.2 million, based on an offering price of $25.00 per share, the midpoint of the range set forth on the cover of this prospectus, after deducting estimated underwriting discounts and commissions and estimated offering expenses.

        We are required under the terms of our Wind Acquisition Loan (which had a variable interest rate of 5.01% at September 30, 2010 and matures in June 2011) to make a principal payment estimated to be approximately $15 to $20 million as a result of this offering. Additionally, we intend to use approximately $78 million of net proceeds from this offering to retire the First Wind Term Loan (which has a fixed interest rate of 17%) in March 2011 in advance of its March 2013 maturity. We intend to use the remainder of the offering proceeds to fund a portion of our project development and construction costs for 2010-2013 and for general corporate purposes.

        A $1.00 increase or decrease in the assumed initial public offering price of $25.00 would increase or decrease net proceeds to us from this offering by approximately $11.2 million after deducting estimated underwriting discounts and commissions and estimated offering expenses.

DIVIDEND POLICY

        We do not expect to declare or pay any cash or other dividends on our Class A common stock, as we intend to reinvest cash flow generated by operations in our business. Our debt agreements effectively limit our ability to pay dividends on our Class A common stock, and we may also enter into credit agreements or other arrangements in the future that prohibit or restrict our ability to declare or pay dividends on our Class A common stock. Class B common stock will not be entitled to any dividend payments.

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CAPITALIZATION

        The following table sets forth the consolidated capitalization of:

•

First Wind Holdings, LLC on an actual basis as of September 30, 2010;



•

First Wind Holdings Inc. on a pro forma basis as of September 30, 2010 to give effect to all of the reorganization transactions described in "The Reorganization and Our Holding Company Structure;" and



•

First Wind Holdings Inc. on a pro forma as adjusted basis as of September 30, 2010 to give further effect to our sale of shares of common stock in this offering at an assumed initial public offering price of $25.00 per share, the midpoint of the range set forth on the cover of this prospectus, after deducting estimated underwriting discounts and commissions and estimated offering expenses.

        You should read this table together with the information under "Unaudited Pro Forma Financial Information," "Selected Historical Financial and Operating Data," "Management's Discussion and Analysis of Financial Condition and Results of Operations," "The Reorganization and Our Holding Company Structure," "Description of Capital Stock" and in the consolidated financial statements included elsewhere in this prospectus.

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DILUTION

        At September 30, 2010 after giving effect to the reorganization described under "The Reorganization and Our Holding Company Structure," the net tangible book value per share of our Class A and Class B common stock was $22.02. Net tangible book value per share is determined by dividing our tangible net worth (tangible assets less total liabilities) by the total number of outstanding shares of Class A and Class B common stock. After giving effect to the sale of shares in this offering at an assumed offering price of $25.00 per share, the midpoint of the range set forth on the cover of this prospectus, after deducting estimated underwriting discounts and commissions and estimated offering expenses, and assuming all Series B Membership Interests that will be outstanding immediately after the reorganization are, together with an equal number of shares of our Class B common stock, exchanged for an equal number of shares of Class A common stock, our net tangible book value at September 30, 2010 would have been approximately $22.25 per share. This represents an immediate dilution of $2.75 per share to new investors purchasing Class A common stock in this offering, resulting from the difference between the offering price and the net tangible book value after this offering. The following table illustrates the per share dilution to new investors purchasing Class A common stock in this offering:

        The following table sets forth at September 30, 2010 after giving effect to the reorganization, the total number of shares of Class A common stock purchased from us, and the total consideration and average price per share paid by existing equity holders and by new investors purchasing Class A common stock in this offering, assuming all Series B Membership Interests that will be outstanding immediately after the completion of the reorganization are, together with an equal number of shares of Class B common stock, exchanged for an equal number of shares of Class A common stock, at an assumed initial public offering price of $25.00 per share, the midpoint of the range set forth on the cover of this prospectus.

        If the underwriters' over-allotment option is exercised in full, the number of shares held by existing stockholders after this offering would decrease to 48.0% of the total number of shares of Class A common stock outstanding immediately following this offering, and the number of shares held by new investors would increase to 13,800,000 or approximately 52.0% of the total number of shares of Class A common stock outstanding immediately following this offering.

        A $1.00 increase (decrease) in the assumed initial public offering price of $25.00 per share would increase (decrease) total consideration paid by new investors in this offering and by all investors by $11.2 million, and dilution per share for new investors by approximately $0.23.

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UNAUDITED PRO FORMA FINANCIAL INFORMATION

        The following unaudited consolidated pro forma statements of operations for the year ended December 31, 2009 and the nine months ended September 30, 2010 and the unaudited pro forma consolidated balance sheet as of September 30, 2010 present our consolidated results of operations and financial position to give pro forma effect to the reorganization transactions described in "The Reorganization and Our Holding Company Structure" and the sale of shares in this offering (excluding shares issuable upon any exercise of the underwriters' over-allotment option) and the application of the net proceeds from this offering as if all such transactions had been completed as of January 1, 2009 with respect to the unaudited consolidated pro forma statement of operations data and as of September 30, 2010 with respect to the unaudited pro forma consolidated balance sheet data. The unaudited pro forma consolidated financial statements reflect pro forma adjustments that are described in the accompanying notes and are based on available information and certain assumptions we believe are reasonable, but are subject to change. We have made, in our opinion, all adjustments that are necessary to present fairly the pro forma financial data.

        The unaudited pro forma financial data are presented for informational purposes only and should not be considered indicative of actual results of operations that would have been achieved had the reorganization transactions and this offering been consummated on the dates indicated, and do not purport to be indicative of statements of financial condition or results of operations as of any future date or any future period.

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FIRST WIND HOLDINGS INC.
Unaudited Pro Forma Consolidated Balance Sheet
As of September 30, 2010
(in thousands, except share amounts)

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FIRST WIND HOLDINGS INC.
Unaudited Pro Forma Consolidated Statement of Operations
Year Ended December 31, 2009
(in thousands, except share and per share amounts)

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FIRST WIND HOLDINGS INC.
Unaudited Pro Forma Consolidated Statement of Operations
Nine Months Ended September 30, 2010
(in thousands, except share and per share amounts)

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SELECTED HISTORICAL FINANCIAL AND OPERATING DATA

        You should read the following selected consolidated financial data together with "Management's Discussion and Analysis of Financial Condition and Results of Operations" and our consolidated financial statements and notes thereto appearing elsewhere in this prospectus. The selected consolidated statement of operations data for the years ended December 31, 2007, 2008 and 2009 and the selected consolidated balance sheet data as of December 31, 2008 and 2009 are derived from our audited consolidated financial statements included elsewhere in this prospectus. The selected consolidated statement of operations data for the nine months ended September 30, 2009 and 2010 and the selected consolidated balance sheet data as of September 30, 2010 are derived from our unaudited interim consolidated financial statements included elsewhere in this prospectus. The unaudited interim period financial information, in the opinion of management, includes all adjustments, which are normal and recurring in nature, necessary for the fair presentation of the periods shown. The selected consolidated statement of operations data for the years ended December 31, 2005 and 2006 and the selected consolidated balance sheet data as of December 31, 2005, 2006 and 2007 are derived from our audited consolidated financial statements not included in this prospectus. Our historical results may not be indicative of the operating results to be expected in any future periods.

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