New study shows large urban roofs best option for community solar

As California policymakers consider the state’s new community solar program and craft a state budget, new research shows that building community solar on commercial and industrial rooftops in urban areas will be more valuable to utility ratepayers than those sited on open land in rural areas.

The new report, conducted by The Brattle Group and commissioned by Solar Landscape, indicates that locating community solar+storage (CSS) projects on large commercial and industrial rooftops in urban areas could create as much as 9.05 ¢/kWh more ratepayer value.

The report examines the incremental quantifiable value that rooftop CSS projects located close to urban and suburban load centers could provide to California, over and above the substantial value provided by ground-mounted CSS projects located in rural areas.

In addition to these quantifiable benefits, the study also found that urban and suburban rooftop CSS projects are likely to create additional hard-to-quantify benefits, including preserving open land, workforce and societal value, and faster project development timelines.

“As California gets serious about deploying community solar and storage to make our grid more reliable and to combat climate change, it makes sense to build that clean energy on large urban roofs, like warehouses, close to where the power demand is,” said Susannah Churchill, Solar Landscape’s Western policy director. “These findings show that locating community solar + storage in our cities will create meaningful additional value for ratepayers. As leaders in Sacramento negotiate the state budget by June 15, we urge Gov. [Gavin] Newsom and the State Assembly and Senate to allocate funding to support locating clean energy and batteries on thousands of large commercial and industrial rooftops.”

Other clean energy advocates also support the advantages of putting community solar on large warehouses.

 Environment California Research & Policy Center recently released a report advocating for building solar on the roofs of warehouses and distribution centers across the country. That report found that California has more warehouse roof potential than any other state, boasting over 66,000 eligible commercial roofs that could power 4.9 million households with solar.

 “California urgently needs more clean energy to avoid the risk of blackouts and reduce pollution, and some of the best sites available are on top of thousands of flat, open, sunny warehouse roofs,” said Laura Deehan, state director of Environment California. “Our state leaders should take note of the opportunity these roofs offer and ensure there’s funding to support building community solar+storage in our cities.”

Report details

The Brattle Group used modeled solar+storage dispatch profiles and hourly avoided costs in various categories from the California Public Utilities Commission (CPUC)’s most recent Avoided Cost Calculator (ACC) to compute the average incremental value of commercial/industrial rooftop community solar plus storage (CSS) projects in urban areas relative to ground-mounted CSS projects in rural areas in each utility region.

The Brattle Group’s study found that commercial/industrial rooftop CSS projects located in urban areas will provide significant incremental value for utility ratepayers relative to ground-mounted CSS projects in rural areas. The specific ratepayer values that Brattle quantified were energy value, capacity value, GHG value, and transmission and distribution value.

When the quantitative values are added together on a 25-year levelized basis, the study concluded that locating community solar plus storage projects on rooftops in urban areas in California could provide additional ratepayer value ranging from 4.39 ¢/kWh (Low Case, SDG&E) to 9.05 ¢/kWh (High Case, SCE) compared with locating those projects on the ground in rural areas. The study also found that in addition to these quantified ratepayer benefits, urban and suburban rooftop CSS projects are likely to create additional hard-to-quantify value streams including land use, workforce and societal value, and faster project development timelines.