We Can Get 40% of Our Electricity Just from Rooftop Solar

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If we put solar on all suitable rooftops in the U.S., how much of our electricity needs would that provide? Nearly 40%, according to a report just out from the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL). 

Where the numbers come from

NREL did a similar study in 2008 and came up with much lower numbers. What’s changed since then?

For one thing, we now have better tools to measure solar rooftop potential. We have much more satellite imagery than we did in 2008, better light detection instruments, and improved data analysis methods and simulation tools. That gives us a much more accurate picture of today’s rooftop solar potential.

Add to that improvements in solar panel efficiency, and you get the new report’s improved numbers.

The importance of small buildings

It’s interesting how significant small buildings are in this calculation. The report found that 83% of small buildings have a suitable location to install solar panels. Even though only 26% of the total rooftop area of those buildings would work for installing panels, there are so many small buildings in the U.S. that they actually provide the greatest potential for solar.

In fact, small buildings could accommodate almost twice as much solar power as medium and large buildings. They could account for about 65% of all rooftop solar in the U.S., compared to 35% from medium and large buildings.

Where we can get the rest of our electricity

So let’s assume we cover all the buildings we can with solar — a pretty far-out assumption to begin with. If that gives us only 40% of the electricity we need, where do we get the rest?

We can turn to the increasingly popular solar canopies over parking lots, where the panels can double as shading for cars. We’re also seeing a lot more solar panels on old landfills or other unusable land. They can even make up part of a farm and coexist peacefully with crops and livestock.

And then, of course, there’s utility-scale solar. As the price of solar outcompetes other fuels, we’re seeing more of these installations around the country. Utility-scale solar will be a crucial part of our move to clean energy, but what’s really interesting about the new report is that it shows how much of a role distributed solar can play, too.