The technical potential for rooftop solar installations on existing buildings throughout the U.S. stands at 1,118 Gigawatt (GW), without taking into account new buildings, canopies over open spaces and “built-in PV”.
This is according to a new report by the National Renewable Energy Laboratory (NREL) says that solar PV rooftops could generate 1,432 Terrawatt hours (TWh) per year, or 39% of U.S.’ electricity sales, a ratio that will increase further as solar module performance improves over time.
For the study, NREL calculated the suitability of rooftops for solar PV installation in 128 cities across the country, representing approximately 23% of U.S. buildings, and then extrapolated these findings to the entire continental US.
Previous analysis by NREL showed a technical potential of just 664 GW and 800 TWh of annual output. The significantly higher updated estimates follow a 3-year research effort and the use of light detection and ranging (LiDAR) data, Geographic Information System methods, and photovoltaic (PV)-generation modeling. Analysts attribute the new findings to a number of factors such as: 1) Advances in module energy density, 2) Improved estimation of building suitability, 3) Higher estimates of the total number of buildings and 4) improvements in solar PV performance simulation tools.
The new report shows that small building rooftops could accommodate as many as 731 GW of solar PV capacity and produce 926 TWh per year. Medium and large buildings have a total installed solar PV capacity potential of 386 GW and an annual power generation potential of 506 TWh.
Geographically, the NREL report suggests very high solar PV potential in California, due to rooftop suitability and relatively high electricity consumption outside the residential sector. In contrast, Florida and other South Atlantic states have high rooftop suitability while lesser non-residential electricity consumption, ranking these states lower on solar PV suitability. Even so, the potential for residential solar PV remains considerable.