Critics claim that there simply isn’t enough land in the U.S. for solar to power the country. While it’s not an immediately practical question, it’s still fun to ponder. So, ignoring practical constraints like storage and grid technology, let’s explore whether we can fit enough solar to electrify the U.S.
One approach would be to start with data points like the size of solar panels, the wattage they produce, and the number of sunny hours per year. Unfortunately, this approach produces wildly different answers depending on assumptions. A better approach is to look at real-world data captured from real-world solar arrays and just extrapolate from there.
Starting with some conservative assumptions from a 2013 National Renewable Energy Labs (NREL) report, we know that it takes, on average, 3.4 acres of solar panels to generate a gigawatt hour of electricity over a year. Given the U.S. consumes about 4 petawatt hours of electricity per year, we’d need about 13,600,000 acres or 21,250 square miles of solar panels to meet the total electricity requirements of the United States for a year.
How much are 21,250 square miles?
This may seem like an impractically large amount of land but not when you put it in perspective. 21,250 square miles is a square about 145 miles on each side . The U.S. has 3,797,000 square miles of land. Only about half a percent of that would be needed to provide enough solar energy to power the country.
Here are some other examples of land use in the range of tens of thousands of square miles:
- 40,223 square miles – this is the size of the land leased by the oil and gas industry (according to the US Bureau of Land Management).
- 18,500 square miles – the amount of federal land offered for lease to the oil and gas industry in 2017 alone.
- 13,000 square miles – the US land that has been impacted by coal surface mining 
- 33,750 square miles – this is the land set aside to grow the corn used to make ethanol, a gasoline substitute .
- 17,120 square miles – the estimated surface area of US roads (8.8 million lane-miles at an average 10 feet wide).
- 70,312 square miles – the total amount of US land used for lawns .
- 22,000 square miles – the size of the Mojave desert, located in southeast California.
- 2,200 square miles – the amount of Appalachian forests that have been cleared for mountaintop removal coal mining by 2012.
- 3,590 square miles – a best guess at how much land is used for parking lots.
Actually, we probably only need about 10,000 square miles
Fortunately, we wouldn’t need to use all 21,250 square miles. NREL has another report conservatively estimating that rooftop solar alone could generate 34% of all U.S. electricity requirements.
Additionally, the solar arrays in NREL’s 2013 survey had efficiency levels of 13-14%. Modern solar panels average 16-17% efficient with widely available models easily exceeding 20%. Revising the estimates using higher efficiency and including rooftop coverage, only 10,000 square miles is required.
Interestingly, Elon Musk shared a nearly identical metric during a speech to the National Governors Association.
“If you wanted to power the entire U.S. with solar panels, it would take a fairly small corner of Nevada or Texas or Utah; you only need about 100 miles by 100 miles of solar panels to power the entire United States. The batteries you need to store the energy, to make sure you have 24/7 power, is 1 mile by 1 mile. One square-mile. That’s it.” — Elon Musk
The Freeing Energy Perspective
Between land and rooftops, there is more than enough space to build all the solar panels necessary to power the United States. Realistically, though, the future of clean energy won’t be entirely solar. Hydro, geothermal, and, particularly, wind, will contribute their fair share as well. But, if we want to move quickly, solar is the fastest path to clean energy. It can be installed as small, easier-to-finance projects. It can be built faster than any other kind of energy. Solar’s small footprint projects are easier to permit and there are more places to put them. Unlike wind and hydro, solar can be built in virtually every state, town, and county in the country. And, as the cost of battery storage continues to decline, it will quickly become feasible to store daytime solar energy for use at night.
- LandArt analyzed the amount of solar required to power the world and produced a great infographic (read here).
- The original NREL analysis (here).
- Renewable Energy World: New study shows 25% of Europe can be powered by rooftop solar