By Katherine Tweed
The National Renewable Energy Laboratory has found that nearly 40 percent of electricity in the U.S. could come from rooftop solar photovoltaics, according to a new study.
The total figure, 1,118 gigawatts, is nearly double the previous estimate of 664 gigawatts that NREL calculated in 2008. The increase is due mostly to increasing module power density, more granular data and a better grasp of building suitability for solar.
“This report is the culmination of a three-year research effort and represents a significant advancement in our understanding of the potential for rooftop PV to contribute to meeting U.S. electricity demand,” Robert Margolis, NREL senior energy analyst and co-author of the report, said in a statement.
NREL brought together ZIP-code-level data with rooftop suitability characteristics, including light detection and ranging (lidar) data and technical generation potential, to model the rooftop PV capacity of 128 cities. Those cities represent about one-quarter of the building stock in the U.S. and 40 percent of the population. NREL then ran two models, one for small buildings under 5,000 square feet and another for medium-size and larger buildings.
When it came to cities with the highest potential for rooftop PV to meet estimated city consumption, California unsurprisingly topped the list, with Mission Viejo, Calif. having a solar potential rating of 88 percent. But just behind Mission Viejo was Concord, New Hampshire at 72 percent, and Buffalo, New York wasn’t far behind at 68 percent. Although only about one-quarter of the rooftop area on small buildings was suitable for solar PV in the U.S., that still equated to more than 900 terawatt-hours per year of energy.
A key factor determining a state’s overall potential for solar PV to offset electricity generation was the per-capita energy consumption. The top six states, NREL noted, all have significantly below-average levels of household energy consumption. For any state that wants to make the most of solar incentives, energy efficiency should also be a top priority.