City rooftops could supply nearly 40 percent of US power, study says

Rooftops could be the next big bet for bringing clean energy to more United States households.

The National Renewable Energy Laboratory released a report in March that said if we slathered viable American rooftops with solar panels, the U.S. could potentially produce enough energy to cover 39 percent of the electricity we consume annually.

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That's about 1,118 gigawatts worth of power. Specifically the report hones in on an unlikely candidate: Small rooftops. "Although only 26 percent of the total rooftop area on small buildings (those with a footprint smaller than 5,000 square feet) is suitable for [photovoltaic systems] deployment, the sheer number of buildings in this class gives small buildings the greatest technical potential," the NREL wrote. The study said small buildings represent 65 percent of rooftop technical potential.

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The study mapped 128 cities over three years to find out how many rooftops would be suitable for solar panels. In particular, the study found Mission Viejo, California; Concord, New Hampshire; Sacramento, California; and Buffalo, New York, could become especially energy efficient if solar panels were deployed on more roofs. According to the study, Mission Viejo could meet 88 percent of the city's own estimated consumption, while Concord could meet around 72 percent of its estimated consumption.

While spreading solar panels to more rooftops could put a lot more clean energy on the grid, there are still other opportunities to expand solar energy production, report co-author Robert Margolis highlighted in a press release.

"It is important to note that this report only estimates the potential from existing, suitable rooftops, and does not consider the immense potential of ground-mounted [photovoltaic systems]," said Margolis, a senior energy analyst at NREL. He said installing solar panels on parking lot canopies, car ports or on the sides of buildings could unlock even more solar energy in urban areas.

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