Resi solar projects are getting larger, increasingly are paired with energy storage

September 13, 2022 at 11:40 AM EDT

Solar-plus-storage adoption in Texas surged in 2021, but Hawaii easily retained its top ranking.

The Energy Department’s Berkeley Lab’s published its latest Tracking the Sun annual report, which is based on data from roughly 2.5 million systems installed nationally through year-end 2021. It includes preliminary data for the first half of 2022.

Key findings include:

Residential systems are getting larger. Residential system sizes have been rising steadily over the past two decades, the report said. This is being driven by declining costs and rising module efficiencies.

As of 2021, the median size of new residential installs was 7.0 kW, compared to 2.4 kW in 2000. Non-residential systems have also grown progressively larger over time, although typical system sizes have plateaued in recent years. The median size of non-residential systems in 2021 was 33 kW and the average size was 255 kW.

System Size Trends over Time

More PV systems are being paired with storage. In 2021, 10% of all new residential PV installations and 5% of all non-residential installations included battery storage.

Hawaii has the highest attachment rate, with more than 90% of new residential installations in 2021 paired with storage. Attachment rates in California were also relatively high (11%), and other pockets of activity emerged in 2021. For example, following Winter Storm Uri in Texas, PV+storage attachment rates rose to 14% in CenterPoint’s service territory.

In addition, storage is increasingly being added to pre-existing PV systems. In 2021, 15% of all new paired PV+storage systems in the U.S. were the result of storage retrofits onto existing PV systems.

Storage sizes are increasing for paired residential systems, and decreasing for non-residential systems. Storage systems in paired residential applications are getting larger, reflecting growing demand for backup power. The report said that 42% of all paired residential installs in 2021 consisted of at least 10 kW of battery storage.

In contrast, paired non-residential systems have been trending toward smaller storage sizes, as uptake expands into applications beyond demand charge management for large commercial & industrial customers.

PV system prices have continued to fall, when adjusting for inflation. In real dollar terms, median installed prices for stand-alone PV systems fell by 10-20 cents per watt, from 2020-2021, across residential and non-residential customer classes. The report said that was consistent with the trajectory seen over most of the past decade.

In the first half of 2022, real prices held flat for residential customers, and fell by 10-30 cents per watt for non-residential customers, depending on project size. These prices represent the up-front price paid by the customer, prior to receipt of any incentives, and can include loan-financing fees bundled into the prices charged by installers.

National Installed-Price Trends over Time. The report defined “large non-residential” systems as being larger than 100 kW, and capped at 5 MW if ground-mounted.

PV system prices vary widely across individual projects. Among stand-alone PV systems without storage, installed prices vary by almost $2/W between the 20th and 80th percentile values for both residential and small non-residential customers, and by roughly $1.5/W for large non-residential customers.

The report said that pricing variability reflects differences in project characteristics as well as features of the local market, policy, and regulatory environment. Adding storage further amplifies pricing variability. Among paired residential projects installed in 2021, average storage costs were roughly $1,200 per kilowatt-hour of storage capacity (equating to an additional $1.9 per watt of PV).

Installed-Price Distributions for Stand-Alone PV Systems Installed in 2021.

The U.S. Department of Energy Solar Energy Technologies Office supported the research work, and multiple individuals and organizations provided data.