If we covered every suitable rooftop in the U.S. with solar panels, how much energy could we generate? The answer is pretty astounding: Enough to meet 39% of total demand, says a U.S. National Renewable Energy Laboratory report.
The new report employs new methods and data to update NREL's estimate of rooftop potential. Its previous best guess was 664 gigawatts (GW) of installed capacity, compared to the 1,118 GW it thinks is possible now.
NREL researchers took light detection and ranging (LiDAR) data for 128 cities nationwide (that is, landscape measurements from a plane fitted with optical remote-sensing equipment) and allied it with mapping software and models of solar generation potential under different conditions. Then they extrapolated results from 128 cities (or 23% of U.S. buildings) for the whole of the country.
The 40% figure is for the country as a whole. In some states, the potential is a good deal higher. California's rooftops could generate 74% of the electricity sold by utilities in 2013. Florida could get 47%. New England states could muster 45%. And even Washington, which has the worst solar resource in the country, could get 27% of its needs met. New York could generate a similar amount to Arizona and Texas, because it has enough buildings.
Certain cities have high solar potential estimates: Concord, New Hampshire (72%), Syracuse, New York (57%), and San Antonio, Texas (51%). (By contrast, New York City can only get 18% of its power from solar panels, and Washington, D.C., only 16%.)
Co-author Robert Margolis, a NREL analyst, says "actual generation from PV in urban areas could exceed these estimates by installing systems on less suitable roof space, by mounting PV on canopies over open spaces such as parking lots, or by integrating PV into building facades."
And, indeed, there's plenty of solar potential beyond rooftop space. Soon solar is likely to be installed in more places, including on the sides of walls and as windows.