What is the potential for rooftop solar?

Rooftop solar systems have the potential to play a significant role in producing electricity in the United States. In a January 2016 report the National Renewable Energy Laboratory (NREL) estimated a total potential for US rooftop photovoltaic power generation at 1,118 GW of installed capacity and 1,432 terawatt-hours (TWh) of annual energy generation. Per the 2022 US Energy Information Administration (EIA) report, the total amount of electrical power generation in the US, both utility scale and distributed solar, was 4,300 TWhs. Thus, rooftop solar has the potential to supply approximately 33% of total US electricity generation.

These results represent a combination of commercial (see Figure 1) and residential (see Figure 2) building potential that takes into consideration average building rooftop footprint, local climate conditions, average module efficiencies, and population densities. California has the highest technical potential with as much as 74% of electricity needs possible from rooftop solar. This is due to its mix of high population (i.e., lots of rooftops) and relatively good solar resource. Figure 3 shows how potential varies by state across the US.

Per the US Energy Information Administration (EIA) Monthly Electric Power Industry Report, June 2023, rooftop solar solar capacity in the US grew from 7.3 GW in 2014, when they started publishing estimates, to 39.5 GW in 2022, with 6.4 GW added in 2022, the most ever in a single year (see Figure 4). The current total represents only 3.5% of the NREL potential capacity, which shows there is a huge, relatively untapped potential for rooftop solar to meet the US renewable energy goals.

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