A solar panel on every roof in the US? Here are the numbers

Enlarge (credit: Jon Callas)

When you're scoping out possible futures, it's useful to ask a lot of "what if?" questions. For example, what if we could install solar panels on every suitable roof in the United States? How much electricity would they generate?

Plenty of research has followed this line of thought, though much of it has necessarily focused on working out the details for individual cities or regions. But now with enough of these studies in the bank, a group of researchers from the US National Renewable Energy Laboratory decided to take another whack at a national estimate.

There are a lot of things you need to know to do this: number of buildings, size of roofs, direction the roofs are facing, strength of sunlight, number of sunny days, and so on. So first off, the researchers took advantage of a Department of Homeland Security program that laser-maps buildings, which now covers almost a quarter of buildings in the US. From this, it's possible to get roof area, roof tilt, roof direction, and whether the roof is shaded by trees. Roofs were tossed out if they were too small, too steep, north-facing, or otherwise would lose more than 20 percent of their possible solar output, but most roofs were suitable.

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