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•	accessing the Internet website specified on your proxy card;

•	calling the toll-free number specified on your proxy card; or

•	signing and returning the enclosed proxy card in the postage-paid envelope provided.

•	by sending a written notice to the Secretary of Tecogen or the Secretary of ADGE, as applicable, at the applicable address set forth below, in time to be received before the Tecogen special meeting or the ADGE special meeting, as applicable, stating that you would like to revoke your proxy;

•	by completing, signing and dating another proxy card and returning it by mail in time to be received before the Tecogen special meeting or the ADGE special meeting, as applicable, or by completing a later dated proxy over the Internet or by telephone, in which case your later dated proxy will be recorded and your earlier proxy revoked; or

•	if you are a holder of record, you can attend the Tecogen special meeting or the ADGE special meeting, as applicable, and vote in person, which will automatically cancel any proxy previously given, or you may revoke your proxy in person, but your attendance alone at the special meeting will not revoke any proxy that you have previously given.

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•	Completion of the Merger is subject to conditions to closing and if these conditions are not satisfied or waived, the Merger will not be completed. Failure to complete the Merger could have material adverse effects on Tecogen and ADGE.

•	The Exchange Ratio is fixed and will not be adjusted in the event of any change in either Tecogen’s or ADGE’s stock price.

•	Failure to complete the Merger could negatively impact the stock prices and future business and financial results of Tecogen and ADGE.

•	The pendency of the Merger could adversely affect the business and operations of Tecogen and ADGE.

•	The ownership percentage of Tecogen and ADGE common stockholders will be diluted by the Merger.

•	Certain of Tecogen’s and ADGE’s respective directors and executive officers have interests in the transactions contemplated by the Merger Agreement that are different from, or in addition to, the interests of Tecogen’s and ADGE’s stockholders generally.

•	If the Merger is approved, the date on which ADGE common stockholders will receive the Merger consideration is uncertain.

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•	adoption of the Merger Agreement and approval of the Merger by ADGE common stockholders;

•	approval of the issuance of the shares of common stock of Tecogen in the Merger contemplated by the Merger Agreement by Tecogen common stockholders;

•	the absence of any law or order by any governmental entity prohibiting, restraining, enjoining or making illegal the consummation of the Merger or the other transactions contemplated by the Merger Agreement;

•	the Form S-4 of which this joint proxy statement/prospectus is a part shall have been declared effective and no stop order suspending the effectiveness of the Form S-4 shall have been issued by the SEC and shall remain in effect and no proceeding to that effect shall have been commenced; and

•	the shares of Tecogen common stock to be issued in connection with the Merger shall have been approved for listing on the Nasdaq Capital Market, subject only to official notice of issuance.

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•	Separate historical financial statements of Tecogen as of and for the year ended December 31, 2016 and the related notes included elsewhere herein; and

•	Separate historical financial statements of ADGE as of and for the year ended December 31, 2016 and the related notes included elsewhere herein.

•	application of the acquisition method of accounting in connection with the Merger to reflect the aggregate purchase consideration;

•	the issuance of Tecogen common shares to the shareholders of ADGE as a portion of the merger consideration;

•	the assumption of equity awards for holders of ADGE’s outstanding equity awards; and

•	transaction costs in connection with the Merger.

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•	market reaction to the announcement of the Merger and Tecogen’s prospects following the Merger effective time;

•	changes in the business, operations, assets, liabilities, financial position and prospects of either company or in market assessments thereof;

•	changes in the operating performance of Tecogen, ADGE or similar companies;

•	changes in market valuations of similar companies;

•	market assessments of the likelihood that the Merger will be completed;

•	interest rates, general market and economic conditions and other factors generally affecting the price of Tecogen’s and ADGE’s common stock;

•	federal, state and local legislation, governmental regulation and legal developments in the businesses in which ADGE and Tecogen operate;

•	dissident stockholder activity;

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•	changes that affect Tecogen’s and ADGE’s industry, the U.S. or global economy, or capital, financial or securities markets generally; and

•	other factors beyond the control of either Tecogen or ADGE, including those described or referred to elsewhere in these “Risk Factors.”

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If the market price of Tecogen common stock declines between the date the Merger Agreement was signed or the date of the ADGE special meeting and the Merger effective time, ADGE stockholders will receive shares of Tecogen common stock that have a market value upon completion of the Merger that is less than the market value of such shares calculated pursuant to the Exchange Ratio on the date the Merger Agreement was signed or on the date of the ADGE special meeting, respectively.

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If the market price of Tecogen common stock increases between the date the Merger Agreement was signed or the date of the Tecogen special meeting and the Merger effective time, ADGE stockholders will receive shares of Tecogen common stock that have a market value upon completion of the Merger that is greater than the market value of such shares calculated pursuant to the Exchange Ratio when the Merger Agreement was signed or the date of the Tecogen special meeting, respectively.

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•	Tecogen and ADGE may experience negative reactions from the financial markets, including negative impacts on the stock prices and debt instruments of ADGE or Tecogen;

•	Tecogen and ADGE may experience negative reactions from their respective customers and employees;

•	Tecogen and ADGE will be required to pay certain costs relating to the transaction, whether or not the transaction is completed;

•

the Merger Agreement places certain restrictions on the conduct of Tecogen’s and ADGE’s businesses prior to completion of the transaction. Such restrictions, the waiver of which is subject to the consent of the other party (not to be unreasonably withheld, conditioned or delayed), may prevent Tecogen or ADGE from making certain acquisitions or taking other specified actions during the pendency of the transaction;

•	matters relating to the transaction (including integration planning) will require substantial commitments of time and resources by Tecogen’s and ADGE’s management, which would otherwise have been devoted to day-to-day operations and other opportunities that may have been beneficial to either Tecogen or ADGE as an independent company.

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•	combining the companies’ corporate functions;

•	combining Tecogen’s and ADGE’s businesses in a manner that permits Tecogen to achieve the synergies anticipated to result from the transaction, the failure of which would result in the anticipated benefits of the transaction not being realized in the time frame currently anticipated or at all;

•	maintaining existing agreements with customers, distributors, and vendors and avoiding delays in entering into new agreements with prospective customers, distributors, and vendors;

•	determining whether and how to address possible differences in corporate cultures and management philosophies;

•	integrating fully the companies’ administrative and technology infrastructures; and

•	effecting potential actions that may be required in connection with obtaining regulatory approvals.

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•	results and timing of our product development;

•	results of the development of our competitors’ products;

•	regulatory actions with respect to our products or our competitors’ products;

•	actual or anticipated fluctuations in our financial condition and operating results;

•	actual or anticipated changes in our growth rate relative to our competitors;

•	actual or anticipated fluctuations in our competitors’ operating results or changes in their growth rate;

•	competition from existing products or new products that may emerge;

•	announcements by us or our competitors of significant acquisitions, strategic partnerships, joint ventures, collaborations, or capital commitments;

•	issuance of new or updated research or reports by securities analysts;

•	fluctuations in the valuation of companies perceived by investors to be comparable to us;

•	share price and volume fluctuations attributable to inconsistent trading volume levels of our shares;

•	additions or departures of key management or personnel;

•	disputes or other developments related to proprietary rights, including patents, litigation matters, and our ability to obtain, maintain, defend or enforce proprietary rights relating to our products and technologies;

•	announcement or expectation of additional financing efforts;

•	sales of our Common Stock by us, our insiders, or our other stockholders; and

•	general economic and market conditions.

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•	have an auditor report on our internal controls over financial reporting pursuant to Section 404(b) of the Sarbanes-Oxley Act;

•	comply with any requirement that may be adopted by the Public Company Accounting Oversight Board regarding mandatory audit ```firm rotation or a supplement to the auditor’s report providing additional information about the audit and the financial statements (i.e., an auditor discussion and analysis);

•	submit certain executive compensation matters to shareholder non-binding advisory votes;

•	submit for shareholder approval golden parachute payments not previously approved; and

•	disclose certain executive compensation related items such as the correlation between executive compensation and financial performance and comparisons of the Chief Executive Officer’s compensation to median employee compensation, when such disclosure requirements are adopted.

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•	the possibility that the proposed transactions will not close, including for failure to obtain applicable stockholder approvals or the failure to satisfy other closing conditions under the Merger Agreement or by the termination of the Merger Agreement;

•	the possibility that the anticipated benefits from the Merger may not be realized or may take longer to realize than expected;

•	unexpected costs or unexpected liabilities that may arise from the transactions contemplated by the Merger Agreement, whether or not completed;

•	each company’s success in implementing its business strategy and its ability to identify, underwrite, finance, consummate and integrate diversifying acquisitions or investments;

•	increases in each company’s cost of borrowing as a result of changes in interest rates and other factors;

•	each company’s ability to pay down, refinance, restructure and/or extend its indebtedness as it becomes due;

•	the outcome of any legal proceedings instituted against Tecogen, ADGE or others following announcement or completion of the Merger;

•	the nature and extent of future competition; and

•	changes in general economic conditions and/or economic conditions in the markets in which each company may, from time to time, compete and the effect of those changes on the company’s revenues and its ability to access the capital markets or other sources of funds.

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•	Internet. Tecogen stockholders may vote over the Internet by going to the website listed on their proxy card or voting instruction form. Once at the website, they should follow the instructions to vote.

•	Telephone. Tecogen stockholders may vote using the toll-free number listed on their proxy card or voting instruction form.

•	Mail. Tecogen stockholders may vote by completing, signing, dating and returning their proxy card or voting instruction form in the pre-addressed postage paid envelope provided.

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•	by sending a written notice to the Secretary of Tecogen at 45 First Ave, Waltham, MA 02451 in time to be received before the Tecogen special meeting stating that you would like to revoke your proxy;

•	by completing, signing and dating another proxy card and returning it by mail in time to be received before the Tecogen special meeting or by completing a later dated proxy over the Internet or by telephone, in which case your later dated proxy will be recorded and your earlier proxy revoked; or

•	if you are a holder of record, you can attend the Tecogen special meeting and vote in person, which will automatically cancel any proxy previously given, or you may revoke your proxy in person, but your attendance alone at the special meeting will not revoke any proxy that you have previously given.

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•	Internet. ADGE stockholders may vote over the Internet by going to the website listed on their proxy card or voting instruction form. Once at the website, they should follow the instructions to vote.

•	Telephone. ADGE stockholders may vote using the toll-free number listed on their proxy card or voting instruction form.

•	Mail. ADGE stockholders may vote by completing, signing, dating and returning their proxy card or voting instruction form in the pre-addressed postage paid envelope provided.

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•	by sending a written notice to the Secretary of ADGE at 45 First Avenue, Waltham, MA 02451 in time to be received before the ADGE special meeting stating that you would like to revoke your proxy;

•	by completing, signing and dating another proxy card and returning it by mail in time to be received before the ADGE special meeting or by completing a later dated proxy over the Internet or by telephone, in which case your later dated proxy will be recorded and your earlier proxy revoked; or

•	if you are a holder of record, you can attend the ADGE special meeting and vote in person, which will automatically cancel any proxy previously given, or you may revoke your proxy in person, but your attendance alone at the special meeting will not revoke any proxy that you have previously given.

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Potential for Contract Renegotiations. Because ADGE will be the surviving corporation in the Merger, the parties do not believe that the Merger will trigger contractual provisions prohibiting the assignment of ADGE’s on-site utility customer contracts. It is possible, however, that some customers may seek to renegotiate their contracts on the basis that the Merger constitutes a prohibited assignment or that the Merger triggers change of control provisions.

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EuroSite Installation Guarantees. ADGE has provided an operational and warranty-type guarantee for the seven EuroSite Power Inc., or Eurosite Power, installations that utilize Tecogen equipment. Despite the transfer of ADGE’s interest in EuroSite Power, ADGE will still be bound by this guarantee of site performance. An off balance sheet reserve may need to be set up to account for this contingent liability.

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EuroSite Convertible Debt Guarantee. ADGE guaranteed on a subordinated basis all amounts payable for EuroSite Power’s 4% Senior Unsecured Convertible Notes. These notes, totaling $300,000, are due in April 2018. Among other things, the guarantees provide that in the event of EuroSite Power's failure to pay principal or interest, the noteholder, subject to the terms and conditions set forth in an Amended Noteholder Agreement, may proceed directly against ADGE, as guarantor, to enforce the guarantee without first proceeding against EuroSite Power. If ADGE were required to pay the debt, however, it would be subrogated to the note holders’ rights.

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EuroSite Power Project Financing Guarantees. In conjunction with EuroSite Power’s project financing agreement with Société Générale Equipment Finance (SGEF), ADGE provided a parent company guarantee of EuroSite Power’s repayment obligations. This guarantee is for an initial 12 month term (ending March 2017) and is cancelable by advance notice given by ADGE to SGEF. Such notice has been given to SGEF by ADGE and became effective February 2017. This guarantee would require payment by ADGE only after efforts to collect from EuroSite Power’s customer and EuroSite Power itself have failed. Total amount borrowed to date under this financing arrangement is approximately $280,000. An off balance sheet reserve may be set up to account for the contingent liability.

•	John Hatsopoulos is the co-Chief Executive Officer of both Tecogen and ADGE.

•	Benjamin Locke is the co-Chief Executive Officer of both Tecogen and ADGE.

•	Robert Panora is the President and Chief Operation Officer of Tecogen and General Manager of ADGE.

•	John Hatsopoulos is a member of the Board of Directors for both Tecogen and ADGE

•	Charles Maxwell is a member of the Board of Directors for Tecogen and Chairman of the Board of Directors of ADGE.

•	The following directors and executive officers of Tecogen and ADGE own a potentially material amount of both ADGE and Tecogen common stock.

◦	John Hatsopoulos beneficially owns more than approximately 16% of Tecogen and 1% of ADGE.

◦	Charles Maxwell beneficially owns approximately 1% of Tecogen and 2% of ADGE.

•	Post merger, the beneficial ownership amount of John Hatsopoulos of Tecogen would decrease from 16% to 13.75%. Charles Maxwell's beneficial ownership of Tecogen would decrease from 1% to 0.90%.

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On August 7, 2015, ADGE entered into a Facilities, Support Services and Business Agreement with Tecogen, or the Facilities Agreement. The Facilities Agreement replaced and amended version of the Facilities and Support Service Agreement, dated as of January 1, 2006 with ADGE. The Facilities Agreement provides that, in exchange for agreed upon fees, Tecogen will provide American DG with, among other things; (1) certain office space; (2) certain business support services; (3) certain rights to purchase cogeneration products directly from the Company at a discounted price; (4) certain rights to purchase Tecogen services at a discounted price; (5) certain rights that allow the ADGE to purchase Tecogen products from Tecogen sales representatives; and (6) the right to certain royalty fees. Absent required notice, the Facilities Agreement will automatically renew for one-month periods. Under this agreement, ADGE leases approximately 2,400 square feet of office space from Tecogen. Under the terms of the Facilities Agreement ADGE pays Tecogen a monthly fee of $5,122 per month.

•	Tecogen is the primary supplier of cogeneration equipment and cogeneration maintenance services to ADGE. Tecogen revenue from sales of cogeneration parts and service to ADGE during the years ended December 31, 2016 and 2015 amounted to $957,760 and $1,903,427, respectively.

•	the low amount of overlapping beneficial ownership of officers and directors of both companies

•	the use of the special committee in the transaction who were empowered to independently negotiate the terms of the Merger and recommend to the board the merits of the Merger,

•	the presence of shared power in the co-CEO role, and

•	the presence and approval of a board of directors made up of a majority of independent members.

•	Fixed Exchange Ratio. The Tecogen Board of Directors required that the Exchange Ratio be fixed and that it will not fluctuate as a result of changes in the price of Tecogen common stock or ADGE common stock. A fixed Exchange Ratio limits the impact of external factors on the transaction.

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Opinion of Financial Advisor. The Tecogen Board of Directors considered the opinion of Scarsdale, dated November 10, 2016, that, as of the date of the Merger Agreement and based upon and subject to the various assumptions made, procedures followed, matters considered and qualifications and limitations on the scope of review undertaken by Scarsdale as set forth in its opinion, the Exchange Ratio of 0.092 of a share of Tecogen common stock for one share of ADGE common stock pursuant to the Merger Agreement was fair, from a financial point of view, to the unaffiliated Tecogen stockholders, as more fully described elsewhere in this joint proxy statement/prospectus.

•	Familiarity with Business. The Tecogen Board of Directors considered its knowledge of the business, operations, financial condition, earnings and prospects of Tecogen and ADGE, taking into account the results of Tecogen’s due diligence review of ADGE, as well as its knowledge of the current and prospective environment in which Tecogen and ADGE operate, including economic and market conditions.

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High Likelihood of Consummation. The Tecogen Board of Directors considered the commitment on the part of both parties to complete the business combination between Tecogen and ADGE pursuant to their respective obligations under the terms of the Merger Agreement. Although there are no voting agreements of any Tecogen or ADGE stockholders to vote for the Merger, given the large insider holdings of both companies, it is believed there is a high likelihood of completion of the transaction.

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Cost Savings and Synergies. The Tecogen Board of Directors considered the management estimates in excess of $750,000 of synergies to be reasonable. Those cost savings included ADGE's reduced administrative costs from the elimination of SEC filing and listing requirements, duplicate personnel and reduced legal costs with a new combined company. Savings from combined service and maintenance fleets are expected to boost margins in operations.

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•	the risk that failure to complete the Merger may negatively affect the price of Tecogen common stock and future business and financial results of Tecogen;

•	the potential risk of diverting management focus and resources from operational matters and other strategic opportunities while working to implement the Merger and related transactions;

•	the risk of not capturing all of the anticipated operational synergies and cost savings between Tecogen and ADGE and the risk that other anticipated benefits might not be realized within the expected time frame or at all;

•	the substantial costs to be incurred in connection with the Merger and related transactions, including the costs of integrating the businesses of Tecogen and ADGE and the transaction expenses to be incurred in connection with the Merger and related transactions;

•	the ability to refinance ADGE’s existing indebtedness and the impact of uncertainty in the capital markets; and

•	the other factors described under “Risk Factors.”

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Competitive Advantage. Bringing ADGE under the Tecogen umbrella would allow a more seamless customer referral process and presents a unified approach to the marketplace in offering clean energy solutions. Tecogen would be able to directly offer customers financing alternatives to an outright equipment purchase. While Tecogen in the past has offered customer referrals to ADGE, the relationship between the two companies was not always clear to customers. With ADGE as a wholly-owned subsidiary, it is expected that Tecogen should be able to eliminate customer concerns related to transparency and potential conflicts-of-interest between the two companies, and verify that every appropriate lead is pursued and closed where possible.

•	Financial Advantage. It is anticipated that the transaction will eliminate significant inter-company expense in consolidation such that the performance of ADGE’s assets will improve in consolidation. Financial advantage is based on the following factors:

◦	Improved Profitability of ADGE Assets. ADGE’s assets are expected to be written down as a result of the Merger. The post-Merger company will benefit from Unfavorable Contract Liability (UCL) accounting methodology which will offset approximately 65% of the annual depreciation expense (from $1.7 million to ~$0.7 million).

◦	Operating cost improvements. The transaction would create operating cost improvements, as follows:

◦	Remove duplicative accounting functions;

◦	Remove duplicative auditing/corporate expenses;

◦	Reduce duplicative engineering and service efforts;

◦	More efficient service inventory; and

◦	As wholly-owned subsidiary, ADGE will no longer incur the expenses of being a publicly traded company.

◦	Enhanced ability to pay off remaining debt

◦	Merged company has better prospects of paying remaining debt; and

◦	Merged company has ability to raise money via equity offering to pay off debt.

◦	More Diversified and Stable Revenue Profile. It is expected that a significant portion of total combined company revenue would be generated by stable long-term contracted revenue streams (Tecogen service revenue plus ADGE energy revenue).

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Investment Advantages. As stockholders of Tecogen, ADGE’s stockholders will participate in possible share price appreciation driven by the growth initiatives related to other Tecogen businesses. Among other things, these Tecogen growth initiatives include development and commercialization of Tecogen’s vehicle emissions control technology, geographic expansion, sales growth related to newly launched products (including the InVerde e+ and the Ilios line of heat pumps).

◦	Eliminate Inefficient Organizational Complexities.

◦	ADGE and Tecogen Serve the Same Markets and Customers. The combination of the companies provides a more compelling value proposition to potential customers. The combination of the two companies into a single company will provide a larger, more economically sound company, which will allow the combined entity to compete more effectively against third parties for new business.

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◦	ADGE Purchases Substantially All of its CHP Units from Tecogen. As Tecogen purchases substantially all of its CHP units from ADGE, combining the companies allows the combined entity to operate in a more cost efficient manner and to better compete on a cost basis for potential customers.

◦	ADGE and Tecogen Share a Management Team. John Hatsopoulos and Benjamin Locke serve as co-CEOs of each of Tecogen and ADGE. In addition, Bonnie Brown, ADGE’s CFO, previously served as CFO of Tecogen. Several of the directors of ADGE also serve as members of the Board of Directors of Tecogen.

◦	ADGE and Tecogen Share Resources. ADGE and Tecogen entered into a Facilities and Support Services Agreement on July 1, 2012 and share facilities, office and other resources. Thus, there will be little disruption in operations caused by the proposed Merger.

◦	that ADGE did not run a competitive auction and weighed against this consideration the views of ADGE’s management, advisors and the Board of Directors that it was highly unlikely that other parties would be interested in acquiring ADGE;

◦	that attempting to close the proposed transaction and integrate the two companies may impact ADGE’s ability to conduct its business in the ordinary course;

◦	the impact on ADGE if the transaction does not close once announced; and

◦	the interests that directors and management have in the transaction.

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•	reviewed a draft of the Merger Agreement dated November 1, 2016;

•	reviewed certain publicly available business and financial information concerning Tecogen, ADGE, and the industries in which they operate;

•	compared the proposed financial terms of the Merger with the publicly available financial terms of certain transactions involving companies we deemed relevant and the consideration paid for such companies;

•	compared the financial and operating performance of Tecogen and ADGE with publicly available information concerning certain other companies we deemed relevant and reviewed the current and historical market prices of Tecogen and ADGE common stock and certain publicly traded securities of such other companies;

•	reviewed certain internal financial analyses and forecasts prepared by or at the direction of the managements of Tecogen and ADGE relating to their respective businesses, as well as the expected amount and timing of the cost savings, related expenses, and synergies expected to result from the Merger; and

•	performed such other financial studies and analyses and considered other information we deemed appropriate for the purposes of this opinion.

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•	Reviewed a draft, received on October 31, 2016, of the Merger Agreement.

•	Reviewed certain publicly available financial information and other data with respect to ADGE and Tecogen that Cassel Salpeter deemed relevant.

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Reviewed certain other information and data with respect to ADGE made available to Cassel Salpeter by ADGE, including financial projections with respect to the future financial performance of ADGE for the years ending December 31, 2016 through December 31, 2020, prepared by management of ADGE or the ADGE Projections, estimates of ADGE’s net operating loss tax carryforwards or the ADGE NOLs, and the potential tax savings available to ADGE based on the ADGE NOLs or the ADGE Estimated NOL Tax Savings, prepared by management of ADGE, and other internal financial information furnished to Cassel Salpeter by or on behalf of ADGE.

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Reviewed certain other information and data with respect to Tecogen made available to Cassel Salpeter by Tecogen, including financial projections with respect to the future financial performance of Tecogen, excluding Tecogen’s interest in the joint venture Ultra Emissions Technologies Inc. or Ultratek, for the years ending December 31, 2016 through December 31, 2018, prepared by management of Tecogen or the Tecogen Projections, estimates of Tecogen’s net operating loss tax carryforwards or the Tecogen NOLs, and the potential tax savings available to Tecogen based on Tecogen NOLs or the Tecogen Estimated NOL Tax Savings, prepared by management of Tecogen, pricing information or the Ultratek Pricing Information, for a recent equity financing effected by Ultratek, and other internal financial information furnished to Cassel Salpeter by or on behalf of Tecogen.

•	Considered and compared the financial and operating performance of ADGE and Tecogen with that of companies with publicly traded equity securities that Cassel Salpeter deemed relevant.

•	Considered the publicly available financial terms of certain transactions that Cassel Salpeter deemed relevant.

•	Discussed the business, operations, and prospects of ADGE, Tecogen and the proposed Merger with ADGE’s and Tecogen’s management and certain of ADGE’s and Tecogen’s representatives.

•	Conducted such other analyses and inquiries, and considered such other information and factors, as Cassel Salpeter deemed appropriate.

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•	Enterprise Value as multiple of revenue for the last twelve months, or “LTM Revenue”;

•	Enterprise Value as a multiple of projected revenue for the year ending December 31, 2016, or “2016 P Revenue”; and

•	Enterprise Value as a multiple of projected revenue for the year ending December 31, 2017, or “2017 P Revenue.”

•	FuelCell Energy Inc.

•	Maxim Power Corp.

•	Polaris Infrastructure Inc.

•	U.S. Geothermal Inc.

•	EuroSite Power Inc.

•	Plug Power Inc.

•	Ballard Power Systems Inc.

•	Advanced Emissions Solutions, Inc.

•	FuelCell Energy Inc.

•	Hydrogenics Corporation

•	Capstone Turbine Corp.

•	Ingersoll-Rand Plc

•	Pentair Plc.

•	AO Smith Corp.

•	Lennox International, Inc.

•	Watts Water Technologies, Inc.

•	AAON Inc.

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	Other Matters Relating to Cassel Salpeter’s Opinion

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•	corporate organization, valid existence, good standing, corporate power and authority, qualification to do business, and organizational documents;

•	capitalization;

•	due authorization of the Merger Agreement and the Merger;

•	validity and binding effect of the Merger Agreement;

•	Board approval of the Merger Agreement, the Merger and other transactions; Board recommendation to stockholders;

•	the absence of a breach or violation of, or a default under, government documents or filing by or obtaining of a permit, authorization, consent or approval of governmental authorities (except as specifically provided);

•	compliance with SEC regulations for periodic reporting;

•	absence of certain changes in the business;

•	absence of material litigation;

•	filing of tax returns and payment of taxes;

•	compliance with law, stock exchange listing and accounting requirements;

•	no undisclosed material liabilities;

•	material compliance with environmental laws and regulations;

•	enforceability and lack of breach of material contracts;

•	absence of material disputes with customers and suppliers;

•	accuracy of the information included herein regarding the company;

•	inapplicability of state anti-takeover statutes; and

•	no appraisal/dissenters’ rights with respect to the Merger.

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•	Tecogen taking all action necessary to cause Merger Sub and the surviving entity to perform their respective obligations under the Merger Agreement and to consummate the Merger and the other transactions contemplated by the Merger Agreement;

•	ADGE taking such steps as may be reasonably necessary or advisable to cause dispositions of ADGE equity securities and the acquisition of Tecogen equity securities pursuant to the transactions contemplated by the Merger Agreement by each ADGE director or officer or who will become a director or officer of Tecogen to be exempt under Rule 16b-3 promulgated under the Exchange Act;

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ADGE promptly notifying Tecogen of any legal proceeding related to the Merger Agreement the Merger or the other transactions contemplated by the Merger Agreement that is brought against ADGE and/or its officers, directors and/or representatives by security holders of ADGE, keeping Tecogen informed on a current basis with respect to the status of any such legal proceeding and providing Tecogen with the opportunity to participate in the defense and settlement of any such legal proceeding, with no settlement thereof being agreed to without Tecogen’s written consent;

•	ADGE using commercially reasonable efforts to cause to be delivered to Tecogen resignations executed by each director of ADGE and its wholly-owned subsidiaries in office immediately prior to the Merger effective time, such resignations to be effective as of the Merger effective time;

•	the parties agreeing to reasonably cooperate in the preparation, execution and filing of all returns, questionnaires, applications or other documents relating to transfer taxes that become payable in connection with the transactions contemplated by the Merger Agreement and to cooperate in attempting to minimize the amount of such transfer taxes;

•	the parties agreeing to use their respective reasonable best efforts to cause the Merger to qualify as a reorganization within the meaning of Section 368(a) of the Internal Revenue Code; and

•	restrictions on both ADGE and Tecogen from declaring a dividend to their respective stockholders after the date of the Merger Agreement, except to the extent consented to in writing by the other party.

•	adoption of the Merger Agreement and approval of the Merger by ADGE common stockholders;

•	approval of the issuance of the shares of Tecogen common stock to be issued in the Merger as contemplated by the Merger Agreement by Tecogen common stockholders;

•	the absence of any law or order by any governmental entity prohibiting, restraining, enjoining or making illegal the consummation of the Merger or the other transactions contemplated by the Merger Agreement;

•	the Form S-4 of which this joint proxy statement/prospectus is a part shall have been declared effective and no stop order suspending the effectiveness of the Form S-4 shall have been issued by the SEC and shall remain in effect and no proceeding to that effect shall have been commenced; and

•	the shares of Tecogen common stock to be issued in connection with the Merger shall have been approved for listing on the Nasdaq Capital Market, subject only to official notice of issuance.

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•	an individual citizen or resident of the United States;

•	a corporation (or any other entity treated as a corporation for U.S. federal income tax purposes) created or organized in or under the laws of the United States, any state thereof or the District of Columbia;

•	an estate the income of which is subject to U.S. federal income taxation regardless of its source; or

•	a trust (i) that is subject to the primary supervision of a court within the United States and all the substantial decisions of which are controlled by one or more U.S. persons or (ii) that has a valid election in effect under applicable U.S. Treasury regulations to be treated as a U.S. person.

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•	will not recognize any gain or loss upon the exchange of shares of ADGE common stock for shares of Tecogen common stock in the Merger;

•	will have a tax basis in Tecogen common stock received in the Merger (including fractional shares for which cash is received) equal to the tax basis of ADGE common stock surrendered in exchange therefore; and

•	will have a holding period for shares of Tecogen common stock received in the Merger (including fractional shares for which cash is received) that includes its holding period for its shares of ADGE common stock surrendered in exchange therefore.

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1.	Third-party laboratory verification.  The AVL California Technology Center, a long-standing research and technology partner with the international automotive industry, confirmed our results in their state-of-the-art dynamometer test cell, which was outfitted with sophisticated emissions measurement equipment.

2.

Verifying longevity and reliability in the field.  By equipping one of our 75 kW units, already operating at a customer location in Southern California with the Ultera low-emissions technology and a device to continuously monitor emissions we verified longevity and reliability. The Ultera low-emissions system operated successfully for more than 25,000 hours, approximately 3.5 years, and consistently complied with California’s stringent emission standards over the entire field testing period.

3.

Additional independent tests.  During the field test, two companies licensed in California to test emissions each verified our results at different times. The results from one of these tests, obtained in August 2011, enabled us to qualify for New Jersey’s fast-track permitting. Virtually every state nationwide requires some kind of permit related to local air quality, but New Jersey allows an exemption for systems such as ours that demonstrate superior emissions performance. This certification was granted in November 2011, and since then we have sold Ultera low-emissions systems to customers in this territory.

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•	Commercial and industrial natural gas fueled engines from other manufacturers

•	Natural gas and biogas powered vehicle fleets - such as municipal bus fleets

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•	Provide power when a utility grid is not available or goes out of service;

•	Reduce the customer’s total cost of purchasing electricity and other fuel;

•	Reduce emissions of criteria pollutants (NOx and CO) to near-zero levels and cut the emission of greenhouse gas such as carbon dioxide;

•	Provide reliable on-site power generation, heating and cooling services; and

•	Control maintenance costs and ensure optimal peak equipment performance.

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•	Sacramento Municipal Utility District has provided test sites for the Company since 2010.

•	Southern California Gas Company and San Diego Gas & Electric Company, each a Sempra Energy subsidiary have granted us research and development contracts since 2004.

•	Department of Energy’s Lawrence Berkeley National Laboratory, research and development contracts executed since 2005, including ongoing Microgrid development work related to the InVerde.

•	Eastern Municipal Water District has co-sponsored demonstration projects to retrofit both a natural-gas powered municipal water pump engine, and a biofuel powered pumping station engine with the Ultera low emissions technology since 2012.

•	Consortium for Electric Reliability Technology Solutions executed research and development contracts, and provided a test site to the Company since 2005.

•	California Energy Commission executed research and development contracts from 2004 until March 2013.

•	The AVL California Technology Center has performed a support role in research and development contracts as well as internal research and development on our emission control system from August 2009 to November 2011. Currently, this testing center's work on emissions from gasoline vehicles which began in January of 2016 continues for the Ultra Emissions joint venture.

•	Propane Education & Research Council (PERC) executed research and development contracts for work related to developing Ultera for the propane powered fork truck market.

•	9,470,126: "Assembly and method for reducing ammonia in exhaust of internal combustion engines." This patent, granted in October 2016, is related to the Ultera emission control system applicable to all of our products.

•	9,121,326: “Assembly and method for reducing nitrogen oxides, carbon monoxide and hydrocarbons in exhausts of internal combustion engines.” This patent, granted in September 2015, is related to the Ultera emission control system applicable to all of our products.

•	8,829,698: “Power generation systems.” This patent, granted in September 2014, is for a power generation system that includes an internal combustion engine configured to provide rotational mechanical energy.

•	8,578,704: “Assembly and method for reducing nitrogen oxides, carbon monoxide, and hydrocarbons in exhausts of internal combustion engines.” This patent, granted in November 2013, is for the Ultera emission system applicable to all our products.

•	7,239,034: “Engine driven power inverter system with cogeneration.” This patent, granted in July 2007, pertains to the utilization of an engine-driven CHP module combined with an inverter and applies to our InVerde product specifically.

•	7,243,017: “Method for controlling internal combustion engine emissions.” This patent, granted in July 2007, applies to the specific algorithms used in our engine controller for metering the fuel usage to obtain the correct combustion mixture and is technology used by most of our engines.

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•	"Systems and methods for reducing emissions in exhaust of vehicles and producing electricity." This patent, filed in November 2015 and published in March 2016, is related to the development of the Ultera emission control system for vehicle applications.

•	“Poison-Resistant Catalyst and Systems Containing Same.” This application, filed in March 2016, relates to treatment of exhaust generated by internal combustion engines, combustion turbines, and boilers and more particularly to systems and method for treating exhausts containing one or more poisons, such as sulfur.

•	“Internal Combustion Engine Controller.” This application, filed in October 2015, relates to controllers and control circuits for controlling an internal combustion engine, including a gas fired internal combustion prime mover used for driving a generator for generating electrical power.

•	“Emissions Control Systems and Methods for Vehicles.” This application, filed in April 2016 relates to emissions control systems for vehicles.

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•	Product safety certifications and interconnection requirements;

•	Air pollution regulations, which govern the emissions allowed in engine exhaust;

•	State and federal incentives for CHP technology;

•	Various local building and permitting codes and third party certifications; and

•	Electric utility pricing and related regulations.

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(1)

Mr. Locke is also the Co-CEO of American DG Energy Inc., and devotes part of his business time to the affairs of American DG Energy. In 2016, $127,400 of his salary was reimbursed by American DG Energy according to the requirements of the business in a given week at a fully burdened rate. On average, Mr. Locke spends approximately 50% of his business time on the affairs of Tecogen, but such amount varies widely depending on the needs of the business.

(2)	Mr. Panora devotes part of his business affairs to American DG Energy. In 2016, $127,400 of his salary was reimbursed by American DG Energy according to the requirements of the business in a given week at a fully burdened rate. On average, Mr. Panora spends approximately 50% of his business time on the affairs of Tecogen, but such amount varies widely depending on the needs of the business.

(3)	Includes stock option award granted May 16, 2016 in connection with Ilios Inc. merger with the Company. Upon completion of the merger all stockholders of Ilios Inc. were given fully vested options of the Company.

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(1)	Includes stock option award granted May 16, 2016 in connection with Ilios Inc. merger with the Company. Upon completion of the merger all stockholders of Ilios Inc. were given fully vested options of the Company.

(2)	Includes stock option award granted on June 3, 2013, with 25% of the shares vesting on June 3, 2014 and then an additional 25% of the shares vesting on each of the subsequent three anniversaries, subject to Mr. Locke's continued employment and subject to acceleration of vesting upon a change in control.

(3)	Includes stock option award granted on December 18, 2014, with 25% of the shares vesting on December 18, 2015 and then an additional 25% of the shares vesting on each of the subsequent three anniversaries, subject to Mr. Locke's continued employment and subject to acceleration of vesting upon a change in control.

(4)

Includes stock option award granted on December 18, 2014, with the shares vesting if the Company achieves a positive adjusted EBITDA for the year ended 2015, modified in December 2015 with 25% of the shares vesting on December 18, 2015 and then an additional 25% of the shares vesting on each of the subsequent three anniversaries, a subject to Mr. Locke's continued employment and subject to acceleration of vesting upon a change in control.

(5)

Includes stock option award granted on February 15, 2011, with 25% of shares vesting on February 15, 2012 and then an additional 25% of the shares vesting on each of the subsequent three anniversaries, subject to Mr. Panora's continued employment and subject to acceleration of vesting upon a change in control. Includes 138,350 shares of restricted Common Stock at a purchase price of $0.001 per share granted on December 4, 2006, 24% shares vesting starting May 20, 2016, subject to acceleration of vesting upon a change in control prior to a termination event.

(6)	Includes stock option award granted May 16, 2016 in connection with Ilios Inc. merger with the Company. Upon completion of the merger all stockholders of Ilios Inc. were given fully vested options of the Company.

(7)	Includes stock option award granted on April 25, 2014, with 255 of the shares vesting on April 25, 2015 and then an additional 25% of the shares vesting on each of the subsequent three anniversaries, subject to Mr. Garrison's continued employment and subject to acceleration of vesting upon a change in control.

(8)	Includes stock option award granted May 16, 2016 in connection with Ilios Inc. merger with the Company. Upon completion of the merger all stockholders of Ilios Inc. were given fully vested options of the Company.

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(1)	Includes stock option award granted May 16, 2016 in connection with Ilios Inc. merger with the Company. Upon completion of the merger all stockholders of Ilios Inc. were given fully vested options of the Company.

(1)

Includes stock option award granted on February 15, 2011, with 25% of the shares vesting on February 15, 2012, and then an additional 25% of the shares vesting on each of the subsequent three anniversaries, provided that Ms. Galiteva serves as a director or consultant to the Company. Includes 25,000 shares of restricted Common Stock at a purchase price of $.004 per share granted on December 13, 2006, with 100% of the shares vesting on May 20, 2017.

(2)	Includes stock option award granted on December 31, 2013, with 25% of the shares vesting on December 31, 2014, and then an additional 25% of the shares vesting on each of the subsequent three anniversaries, provided that Dr. Aoun serves as a director or consultant to the Company.

(3)	Includes stock option award granted May 16, 2016 in connection with Ilios Inc. merger with the Company. Upon completion of the merger all stockholders of Ilios Inc. were given fully vested options of the Company.

(4)	Includes stock option award granted on February 15, 2011, with 25% of the shares vesting on February 15, 2012, and then an additional 25% of the shares vesting on each of the subsequent three anniversaries, provided that Mr. Maxwell serves as a director or consultant to the Company.

(5)	Includes stock option award granted May 16, 2016 in connection with Ilios Inc. merger with the Company. Upon completion of the merger all stockholders of Ilios Inc. were given fully vested options of the Company.

(6)	Includes stock option award granted on September 8, 2014, with 25% of the shares vesting on September 8, 2015, and then an additional 25% of the shares vesting on each of the subsequent three anniversaries.

(7)	Includes stock option award granted on September 2, 2016, with 25% of the shares vesting on September 2, 2017, and then an additional 25% of the shares vesting on each of the subsequent three anniversaries, provided that Mr. Davidson serves as a director on consultant to the Company.

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(1)	The address of the executive officers and directors listed in the table above is: c/o Tecogen Inc., 45 First Avenue, Waltham, Massachusetts, 02451.

(2)

Based solely upon: (a) the Schedule 13G/A filed by Mr. John N. Hatsopoulos on February 14, 2017. The Schedule 13G/A states the beneficial ownership of Mr. Hatsopoulos as the following: (1) 155,351 shares of common stock held directly by Mr. Hatsopoulos; 1,039,480 shares of common stock held by the Nia M. Hatsopoulos Jephson 2011 Irrevocable Trust, for which Mr. Hatsopoulos is the trustee; (3) 1,039,480 shares of common stock held by the Alexander J. Hatsopoulos 2011 Irrevocable Trust, for which Patricia L. Hatsopoulos, Mr. Hatsopoulos' spouse is the trustee; (4) 989,589 shares of common stock held by the John N. Hatsopoulos Family Trust 2007 for the benefit of Patricia L. Hatsopoulos, Alexander J. Hatsopoulos, and Nia Marie Hatsopoulos, for which Dr. George N. Hatsopoulos and Ms. Patricia L. Hatsopoulos are the trustees; and 28,225 shares of common stock held by Patricia L. Hatsopoulos. The address of the holder is 3 Woodcock Lane, Lincoln, MA 01773; and (b) an SEC Form 4 filed on May 18, 2016 12,723 common stock options exercisable within 60 days of March 9, 2017.

(3)

Based solely upon the Schedule 13G filed by Tryfon Natsis and Despina Pantopoulou Natsis on February 1, 2017. The Schedule 13G states the beneficial ownership as the following: 1,616,673 owned jointly by Tryfon Natsis and Despina Pantopoulou Natsis as spouses and joint tenants with the right of survivorship. The address for each holder is 36 Chemin Du Milieu, Collonge-Bellerive, Geneva, Switzerland 1245.

(4)

Based solely upon the Schedule 13G/A filed by Dr. George Hatsopoulos on December 14, 2016. The Schedule 13G/A states the beneficial ownership of Dr. Hatsopoulos as the following: (1) 1,276,604 shares of common stock held directly by Dr. Hatsopoulos; and (2) 78,937 shares of common stock held by Dr. Hatsopoulos and his wife Daphne Hatsopoulos as joint tenants. The address of the holder is 233 Tower Road, Lincoln, MA 01773.

(5)	Based solely upon the Schedule 13D filed by Wincrest Capital Limited on February 13, 2017. The Schedule 13D states the beneficial ownership of Wincrest Capital Limited is as follows: 1,247,165 shares owned directly by Wincrest Capital Limited. The principal business address of the holder is 7 Old Fort Bay Town Centre Nassau, The Bahamas.

(6)	This amount includes: (a) $3,150,000 of convertible debt that is convertible at $3.54 within 60 days of of March 9, 2017; and (b) 307,329 shares of common stock.

(7)	Includes: (a) 150,850 shares of Common Stock, directly held by Mr. Panora, and (b) options to purchase 125,000 shares of Common Stock exercisable within 60 days of March 9, 2017.

(8)	Includes: (a) 107,269 shares of Common Stock, directly held by Mr. Maxwell, and (b) options to purchase 25,000 shares of Common Stock exercisable within 60 days of March 9, 2017.

(9)	Includes 109,375 options to purchase Common Stock exercisable within 60 days of March 9, 2017.

(10)	Includes: (a) 50,000 shares of Common Stock, directly held by Ms. Galiteva and (b) options to purchase 25,000 shares of Common Stock exercisable within 60 days of March 9, 2017.

(11)	Includes: (a) 25,000 shares of Common Stock, directly held by Mr. Ghoniem, and (b) options to purchase 37,723 shares of Common Stock exercisable within 60 days of March 9, 2017.

(12)	Includes: (a) 10,000 shares of Common Stock, directly held by Mr. Garrison, and (b) options to purchase 43,862 shares of Common Stock exercisable within 60 days of March 9, 2017.

(13)	Includes: (a) 9,044 shares of Common Stock, directly held by Mr. Davidson, and options to purchase 12,500 shares of Common Stock exercisable within 60 days of March 9, 2017.

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On May 4, 2016, we entered into an agreement with John Hatsopoulos, our co-Chief Executive Officer, a director and principal stockholder, and another investor to exchange an aggregate of $9.3 million in principal and prepaid interest under outstanding 2014 Senior Unsecured Debentures (“Senior Unsecured Debentures”) held by them for an aggregate of approximately 14.72 million shares of EuroSite owned by us.

•

On June 28, 2016, our ownership interest in EuroSite was reduced to 20.5% as a result of the conversion of substantially all of the outstanding convertible debentures of Eurosite that had been guaranteed by ADGE into shares of common stock of EuroSite. Following such conversion, ADGE accounted for its interest in EuroSite in its consolidated financial statements under the equity method of accounting.

•	On September 30, 2016, holders of our outstanding 6% convertible notes (“convertible notes”) agreed to exchange principal and prepaid interest in the aggregate amount of approximately $4.3 million under such notes for an aggregate of 9,700,000 shares of common stock of EuroSite owned by us.

•

On September 30, 2016, we sold an aggregate of 5,500,000 shares of common stock of EuroSite owned by us to two investors for an aggregate of $2.2 million, the proceeds of which were paid to further reduce the amount of our outstanding convertible notes. As part of such transaction, the former convertible note holders cancelled warrants to purchase an aggregate of 1,020,000 shares of common stock of EuroSite we had issued to such holders.

•	On May 4, 2016, as discussed above, we exchanged an aggregate of $9.3 million in principal and prepaid interest under outstanding Senior Unsecured Debentures for an aggregate of approximately 14.72 million shares of EuroSite owned by us. Following the exchange, the debentures were cancelled.

•

On September 30, 2016, holders of our outstanding 6% convertible notes exchanged $4.3 million in principal and prepaid interest for 9,700,000 shares of EuroSite owned by us and we issued a new note to evidence the remaining balance of the debt of $3,418,681. The prior convertible note was cancelled by us. The new note was upon substantially the same terms as the 6% convertible note and was convertible into our shares at a price of $2.11 per share, subject to certain adjustments in the event of stock splits, stock dividends, and certain other events.

•	On September 30, 2016, as discussed above, we used the $2.2 million proceeds from the sale of 5.5 million shares of EuroSite to further reduce the amount of our outstanding convertible notes.

•	On December 23, 2016, we repaid the remaining outstanding balance of our outstanding convertible notes of approximately $3.1 million (net of prepaid interest).

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Greatly increased overall energy efficiency (up to 90% - see Environmental and Energy Study Institute (EESI), Energy Generation and Distribution Efficiency, available at http://www.eesi.org/generation_distribution. This website address and any other website addresses included herein are included as textual references only and the information in such websites is not incorporated herein by reference.

•	Rapid adaptation to changing demand requirements (e.g., weeks, not years, to add new generating capacity where and when it is needed).

•	Ability to by-pass transmission line and substation bottlenecks in congested service areas.

•	Avoidance of site and right-of-way issues affecting large-scale power generation and distribution projects.

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•	Clean operation, in the case of natural gas fired reciprocating engines using microprocessor combustion controls and low-cost exhaust catalyst technology developed for automobiles.

•	Rapid economic paybacks for equipment investments, as fast as four to six years when compared to existing utility costs and technologies.

•	Decreased sensitivity to fuel prices due to high overall efficiencies achieved with cogeneration of electricity and thermal energy, including the use of waste heat to operate absorption type air conditioning systems (displacing electric-powered cooling capacity at times of peak summer demand).

•	Reduced vulnerability of multiple de-centralized small-scale generating units compared to the risk of major outages from natural disasters or terrorist attacks against large central-station power plants and long distance transmission lines.

•	Ability to remotely monitor, control and dispatch energy services on a real-time basis using advanced switchgear, software, microprocessor and internet modalities. Through our on-site energy products and services, energy users are able to optimize, in real time, the mix of centralized and distributed electricity-generating resources.

•	Energy Sales

◦	Electricity

◦	Thermal (Hot Water, Heat and Cooling)

•	Energy Producing Products

◦	Cogeneration Packages

◦	Chillers

◦	Natural Gas Heat Pumps

◦	Complementary Energy Equipment (e.g., boilers, etc.)

•	Turnkey Installation of Energy Producing Products with Incentives

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•	Guaranteed lower price for energy

•	Only pay for the energy they use

•	No capital costs for equipment, engineering and installation

•	No equipment operating costs for fuel and maintenance

•	Immediate cash flow improvement

•	Significant green impact by the reduction of carbon produced

•	No staffing, operations and equipment responsibility

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On May 4, 2016, we entered into an agreement with John Hatsopoulos, our co-Chief Executive Officer, a director and principal stockholder, and another investor to exchange an aggregate of $9.3 million in principal and prepaid interest under outstanding 2014 Senior Unsecured Debentures (“Senior Unsecured Debentures”) held by them for an aggregate of approximately 14.72 million shares of EuroSite owned by us.

•

On June 28, 2016, our ownership interest in EuroSite was reduced to 20.5% as a result of the conversion of substantially all of the outstanding convertible debentures of Eurosite that had been guaranteed by ADGE into shares of common stock of EuroSite. Following such conversion, ADGE accounted for its interest in EuroSite in its consolidated financial statements under the equity method of accounting.

•	On September 30, 2016, holders of our outstanding 6% convertible notes (“convertible notes”) agreed to exchange principal and prepaid interest in the aggregate amount of approximately $4.3 million under such notes for an aggregate of 9,700,000 shares of common stock of EuroSite owned by us.

•

On September 30, 2016, we sold an aggregate of 5,500,000 shares of common stock of EuroSite owned by us to two investors for an aggregate of $2.2 million, the proceeds of which were paid to further reduce the amount of our outstanding convertible notes. As part of such transaction, the former convertible note holders cancelled warrants to purchase an aggregate of 1,020,000 shares of common stock of EuroSite we had issued to such holders.

•	On May 4, 2016, as discussed above, we exchanged an aggregate of $9.3 million in principal and prepaid interest under outstanding Senior Unsecured Debentures for an aggregate of approximately 14.72 million shares of EuroSite owned by us. Following the exchange, the debentures were cancelled.

•

On September 30, 2016, holders of our outstanding 6% convertible notes exchanged $4.3 million in principal and prepaid interest for 9,700,000 shares of EuroSite owned by us and we issued a new note to evidence the remaining balance of the debt of $3,418,681. The prior convertible note was cancelled by us. The new note was upon substantially the same terms as the 6% convertible note and was convertible into our shares at a price of $2.11 per share, subject to certain adjustments in the event of stock splits, stock dividends, and certain other events.

•	On September 30, 2016, as discussed above, we used the $2.2 million proceeds from the sale of 5.5 million shares of EuroSite to further reduce the amount of our outstanding convertible notes.

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•	On December 23, 2016, we repaid the remaining outstanding balance of our outstanding convertible notes of approximately $3.1 million (net of prepaid interest).

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ARTICLE I THE MERGER	1

Section 1.1 The Merger.	2

Section 1.2 Closing.	2

Section 1.3 Effective Time.	2

Section 1.4 Governing Documents.	2

Section 1.5 Directors and Officers of the Surviving Entity.	2

Section 1.6 Tax Consequences.	2

Section 1.7 Subsequent Actions.	2

ARTICLE II TREATMENT OF SECURITIES	2

Section 2.1 Treatment of Capital Stock.	2

Section 2.2 Payment for Securities; Surrender of Certificates.	3

Section 2.3 Dissenter’s Rights..	5

Section 2.4 Treatment of ADGE Equity Awards.	5

Section 2.5 Withholding.	6

Section 2.6 No Fractional Shares.	6

ARTICLE III REPRESENTATIONS AND WARRANTIES	6

Section 3.1 Organization and Standing.	6

Section 3.2 Capitalization.	6

Section 3.3 Authorization; Validity of Agreement; Company Action.	7

Section 3.4 Board Approvals.	7

Section 3.5 Consents and Approvals; No Violations.	7

Section 3.6 SEC Documents and Financial Statements.	8

Section 3.7 Absence of Certain Changes.	9

Section 3.8 Litigation.	9

Section 3.9 Taxes.	9

Section 3.10 Compliance with Law, Listing and Accounting Requirements.	9

Section 3.11 Information in the Form S-4 and Joint Proxy Statement.	9

Section 3.12 Takeover Statutes.	10

Section 3.13 Dissenters’ Rights.	10

Section 3.14 No Undisclosed Liabilities.	10

Section 3.15 Environmental Laws and Regulations.	10

Section 3.16 Material Contracts.	11

Section 3.17 Customers and Suppliers.	12

Section 3.18 Finders or Brokers.	12

ARTICLE IV CONDUCT OF BUSINESS PENDING THE MERGER	12

Section 4.1 Conduct of Business by ADGE and Tecogen Pending the Closing.	12

Section 4.2 Form S-4 and Joint Proxy Statement.	12

Section 4.3 Stockholder Approval; Majority of the Minority.	14

ARTICLE V ADDITIONAL AGREEMENTS	14

Section 5.1 Access; Confidentiality; Notice of Certain Events.	14

Section 5.2 Consents and Approvals.	15

Section 5.3 Publicity.	16

Section 5.4 Directors’ and Officers’ Insurance and Indemnification.	16

Section 5.5 Takeover Statutes.	17

Section 5.6 Obligations of Merger Sub.	18

Section 5.7 Rule 16b-3.	18

Section 5.8 Security Holder Litigation.	18

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Section 5.9 Director Resignations.	18

Section 5.10 Dividends.	18

Section 5.11 Employee Benefits.	18

ARTICLE VI CONDITIONS TO CONSUMMATION OF THE MERGER	19

Section 6.1 Conditions to Each Party’s Obligations to Effect the Merger.	19

Section 6.2 Conditions to Obligations of Tecogen and Merger Sub.	20

Section 6.3 Conditions to Obligations of ADGE.	20

ARTICLE VII TERMINATION	20

Section 7.1 Termination.	20

Section 7.2 Effect of Termination.	20

Section 7.3 Go-Shop Right.	21

Section 7.4 ADGE Change Election.	21

Section 7.5 Tecogen Change Election.	21

ARTICLE VIII MISCELLANEOUS	22

Section 8.1 Amendment and Modification; Waiver.	22

Section 8.2 Non-Survival of Representations and Warranties.	22

Section 8.3 Expenses.	22

Section 8.4 Notices.	23

Section 8.5 Certain Definitions.	23

Section 8.6 Interpretation.	26

Section 8.7 Counterparts.	26

Section 8.8 Entire Agreement; Third-party Beneficiaries.	27

Section 8.9 Severability.	27

Section 8.10 Governing Law; Jurisdiction.	27

Section 8.11 Waiver of Jury Trial.	27

Section 8.12 Assignment.	27

Section 8.13 Enforcement; Remedies.	28

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(1)	the Company will organize Merger Sub as a Delaware corporation and wholly-owned subsidiary of the Company;

(2)	the Merger Sub will be merged with and into ADGE, with ADGE surviving as a wholly-owned subsidiary of the Company;

(3)

each outstanding share of ADGE common stock, par value $0.001, other than shares of ADGE common stock held by ADGE or any wholly-owned ADGE subsidiary, will be converted into the right to receive a fraction of a share of Company common stock equal to the quotient obtained by dividing (i) $0.38 by (ii) the aggregate volume-weighted average per share closing price of Company common stock on the Nasdaq Capital Market for the 20 consecutive trading days ending October 28, 2016 (the "ADGE Exchange Ratio").

(i)	reviewed a draft of the Agreement dated November 1, 2016;

(ii)	reviewed certain publicly available business and financial information concerning the Company, ADGE, and the industries in which they operate;

(iii)	compared the proposed financial terms of the Transaction with the publicly available financial terms of certain transactions involving companies we deemed relevant and the consideration paid for such companies;

(iv)	compared the financial and operating performance of the Company and ADGE with publicly available information concerning certain other companies we deemed relevant and reviewed the current and historical market prices of the Company and ADGE common stock and certain publicly traded securities of such other companies;

(v)	reviewed certain internal financial analyses and forecasts prepared by or at the direction of the managements of the Company and ADGE relating to their respective businesses, as well as the expected amount and timing of the cost savings, related expenses, and synergies expected to result from the Transaction (the "Synergies"); and

(vi)	performed such other financial studies and analyses and considered other information we deemed appropriate for the purposes of this opinion.

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•	Reviewed a draft, received on October 31, 2016, of the Merger Agreement.

•	Reviewed certain publicly available financial information and other data with respect to the Company and the Acquiror that we deemed relevant.

•

Reviewed certain other information and data with respect to the Company made available to us by the Company, including financial projections with respect to the future financial performance of the Company for the years ending December 31, 2016 through December 31, 2020, prepared by management of the Company (the "Company Projections"), estimates of the Company's net operating loss tax carryforwards ("Company NOLs") and the potential tax savings available to the Company based on the Company NOLs (the "Company Estimated NOL Tax Savings") prepared by management of the Company, and other internal financial information furnished to us by or on behalf of the Company.

•

Reviewed certain other information and data with respect to the Acquiror made available to us by the Acquiror, including financial projections with respect to the future financial performance of the Acquiror, excluding the Acquiror's interest in the joint venture Ultra Emissions Technologies Inc. ("Ultratek"), for the years ending December 31, 2016 through December 31, 2018, prepared by management of the Acquiror (the "Acquiror Projections"), estimates of the Acquiror's net operating loss tax carryforwards (the "Acquiror NOLs") and the potential tax savings available to the Acquiror base on the Acquiror NOLs (the "Acquiror Estimated NOL Tax Savings") prepared by management of the Acquiror, pricing information (the "Ultratek Pricing Information") for a recent equity financing effected by Ultratek, and other internal financial information furnished to us by or on behalf of the Acquiror.

•	Considered and compared the financial and operating performance of the Company and the Acquiror with that of companies with publicly trade equity securities that we deemed relevant.

•	Considered the publicly available financial terms of certain transactions that we deemed relevant.

•	Discussed the business, operations, and prospects of the Company, the Acquiror and the proposed Merger with the Company's and the Acquiror's management and certain of the Company's and the Acquiror's representatives.

•	Conducted such other analyses and inquiries, and considered such other information and factors, as we deemed appropriate.

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•	for any breach of the director's duty of loyalty to the Company or its stockholders;

•	for acts or omissions not in good faith or that involve intentional misconduct or a knowing violation of law;

•	under section 174 of the Delaware General Corporation Law regarding unlawful dividends and stock purchases; or

•	for any transaction from which the director derived an improper personal benefit.

•	we must indemnify our directors and officers to the fullest extent permitted by Delaware law;

•	we may, to the extent authorized from time to time by our Board of Directors, indemnify our other employees and agents to the same extent that we indemnified our officers and directors; and

•	in the event we do not assume the defense in a legal proceeding, we must advance expenses, as incurred, to our directors and executive officers in connection with a legal proceeding to the fullest extent permitted by Delaware law.

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