By Will Driscoll
The continental U.S. could produce 38 percent of its electricity from rooftop solar installations, according to a report from the National Renewable Energy Laboratory (NREL). Yes, that’s a lot:
- It’s 1,118 gigawatts of solar capacity—or almost 80 times the 2016 U.S. solar installations of 14.6 gigawatts.
- Installing that much rooftop solar would yield about two million jobs per year for ten years—that’s eight times the number of U.S. solar jobs in 2016.
The NREL analysis evaluated the potential for solar on buildings with at least one unshaded roof plane that is either nearly flat, or faces east, southeast, south, southwest, or west. If any such roof plane could accommodate at least 1.5 kilowatts of solar panels, NREL modeled solar on that roof plane. Summing across all buildings yielded a technical potential of 1,118 gigawatts of rooftop solar. NREL found that 66 percent of large building rooftop area is suitable for solar, versus 49 percent for medium buildings and 26 percent for small buildings.
The technical potential is simply what the laws of physics allow, combined with common sense—i.e., no north-facing panels. (NREL did count west-facing panels, which have value for meeting late afternoon electricity demand, and east-facing panels, which are equally productive.) NREL assumed an average solar panel efficiency of 16 percent, and noted that if panels averaging 20 percent efficiency were used, the solar potential would be 25 percent greater (because 20 is that much greater than 16). At least three firms make solar panels exceeding 20 percent efficiency.
The technical potential is just a theoretical concept. Yet the economic potential–that is, the rooftop solar installations that would save building owners money–may not be far behind. Especially over the next ten years, as solar costs keep falling due to technology improvements and economies of scale, the economic potential will keep rising. Already, more building owners each year realize they can save money with rooftop solar.
The Solar Energy Industries Association reported 2016 U.S. solar installations of 14.6 gigawatts. Installing NREL’s potential 1,118 gigawatts of rooftop solar over ten years would mean 112 gigawatts per year, or about eight times the amount installed in 2016. The Solar Foundation counted 260,077 U.S. solar workers in 2016, so an eightfold increase from that level would be about 2 million jobs—again, for a ten-year period. Utility-scale solar jobs would be additional. The U.S. construction industry—with 9.6 million jobs in 2015—would far outpace the rooftop solar industry, but rooftop solar would make a solid contribution.
For rooftop installations, the number of jobs per gigawatt installed would arguably be higher than the U.S. average in 2016, because rooftop jobs are smaller and more labor-intensive than utility-scale solar projects. On the other hand, with a big increase in the size of the rooftop solar industry, economies of scale should also come into play. So on balance, a potential two million jobs per year for ten years seems like a good ballpark estimate.
Will Driscoll is a writer and analyst. Previously he conducted environmental analyses for EPA, as a project manager for ICF Consulting. He earned a master’s degree in economics and policy from Princeton.