How much solar would it take to power the U.S.?

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 petawatts 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.

The yellow square is approximately 21,000 square miles. Map courtesy of Google Maps.
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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.
  • 33,750 square miles – this is the land set aside to grow the corn used to make ethanol, a gasoline substitute.
  • 62,500 square miles – the total amount of U.S. 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.
  • 16,000 square miles – this is an estimate of the total surface of U.S. roads, including highways (4.12 million miles of roads that are an average 20 feet wide).

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.

The blue square is approximately 100×100 miles or 10,000 square miles. Maps courtesy of Google Maps.

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

Elon Musk speaking at the National Governors Association in 2017

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. 

Additional reading

  • LandArt analyzed the amount of solar required to power the world and produced a great infographic (read here).
  • The original NREL analysis (here).

20 thoughts on “How much solar would it take to power the U.S.?

  1. What about using solar to power all cars, trucks, etc., if we converted all gas vehicles to electric, and how do we get solar energy to remote locations for all vehicles?
    How much more solar than 101 sq miles?

    1. Great question. I’ll do some quick math here. According to the US Bureau of Transportation statistics, vehicles drove 3.2 trillion miles in 2017. Using a Nissan Leaf as an average, an electric vehicle gets about 30 miles per kilowatt hour. This means it would take 106 billion kilowatt-hours or 106 terawatt-hours or drive those 3.2 trillion miles.

      Since it takes 21,250 square miles of solar for 4 petawatt hours (or 4,000 terawatt hours), each terawatt hour takes about 5.3 square miles per terawatt hour. So, very roughly, if all US cars and trucks converted to electric vehicles, it would take 5.3 square miles x 106 terawatt-hours, or 562 square miles of solar panels to power them all.

      https://www.bts.gov/content/us-vehicle-miles

    2. The first problem is that everything is looked as just needing to change energy source and even needing more energy for population growth. You really need to look at the problem from the beginning. Why do two people or even a family of six need to live in such large houses?

      No one talks about the ridiculous excess that we live, they just talk about continuing on with it and power it all in a different way.

      How many square feet do you really need to sustain life? The way that homes are built for energy efficiency is a complete joke. Why do we need clorinated and heavily filtered swimming pools sitting unused in back yards? How much energy and resourses are used when millions of people are driving millions of miles to huge stadiums where they watch others who are paid outrageous sums to throw balls around or those who do the same to see how fast cars can race around a track.

      Stop and think. It’s pure insanity so let’s all idolize a guy and and and an electric car that can do zero to sixty in 3.5 seconds and reach 160 mph. At the same time this guy is saying save the world from fossil fuels and says how his electric car can out run an ice. Wouldnt the bragging points be about how the new vehicle used minimal resourses to transport people at no more than the legal speed limits? Its insanity.

    3. The rough math — to cover the 3.22 Trillion Miles driven in the US, with about 250 Watt-hours per mile — works out to about a 20% increase.

      But then when you take away all the Electricity now used to Drill, Pump, Refine, and Retail that Oil — as Gasoline and Diesel — the net increase is more likely to be around 10% Net Total — to replace all US Ground Transportation as Electric.

      We normally plan on increasing US Grid and Generation Capacity at least 1 to 2% per year, but recent improvements in LED Lighting and other Energy Conservation is leaving much of the US Grid at surplus, already. So this would all be covered in a few years.

    4. LOL you are using 2013 data in an industry that doubles its efficiency every 2 years !. If it needed 21,000 acres before. Its likely been close to cut in half three times since the 6 year old data. 21,000 down to 10,500. 10,500 down to 5,250. 5250 down to 2,625. I bet my answer is WAYYYYY closer than yours. In 3-4 more years we will have a very good working battery and the acres needed will be manageable. Go do some work. LOL

  2. I think that the title may be a bit misleading… there are lots of energy uses which are not included in that 4 petawatt-hours/year figure (which mearly looks at “electricity usage”.

    Total U.S. energy consumption (all end-uses, so this includes transportation that Steve was asking about as well) is about 97.3 quadrillion BTU or 28.519 petta-watt hours. https://www.eia.gov/state/seds/archive/seds2016.pdf

    That works out to needing about 151,500 square miles (not including battery area) which is nearly the area of California.

    I think this points to the need to pursue a balanced clean-energy portfoilio including solar, wind, batteries, hydro, and nuclear. (it would take around 3,255 square miles of nuclear plants, for example)

    1. Thanks for sharing these insights. I had hoped by using the term “power” rather than “energy” that it would be implied I meant electricity and not all energy sources. Either way, you raise a very intriguing point about the fundamental challenges of accelerating electrification in transportation and industrial heating. Can you point me to some sources that go through more of this math in depth? For example, how does energy to power transportation change (higher or lower) when it becomes electrified? Also, are the EIA data you cite the energy delivered or energy used? For example, for transportation is that data how much energy is used by the vehicles or is the potential energy available in the gasoline before it is combusted? I ask because converting to the equivalent electricity may or may not be 1:1 (because electric motors are more energy efficient than combustion engines)? Thanks for raising this and I look forward to exploring it more.

    2. (I don’t see a reply button on your comment – so I’m commenting above)

      That’s a good point – they seem to be measuring fuel consumption, not energy produced! For transportation (and for heating for that matter) you aren’t getting 100% of the possible heat out of the fuel. Typical modern ICE cars get around 25% thermal efficiency (https://www.researchgate.net/post/what_is_an_efficiency_of_modern_average_car_IC_engines ) by contrast a modern natural gas power plant gets around 62% efficiency. That means that electrifying transportation is a massive savings in carbon even if those cars are charged with natural gas power plants. (around 2.5 times more energy per unit fuel)

      After generator, transmission, distribution, and charging losses – electric vehicles get around 85% of the power that is generated into their batteries (around 15-20% of the power is lost https://www.sciencedirect.com/science/article/pii/S0360544217303730).

      So if transportation makes up 27828 trillion BTU, at ~25% thermal efficiency, only around 2.038 pWh were generated (instead of 8.155). With charging/transmission losses, we’d need to generate about 2.4 pWh to actually charge 2 pWh worth of EVs.

      In other words, you save about 5.75 pWh through increased efficiency by moving away from ICE cars. Reducing your total generation need from 28.5 pWh to 22.75 pWh.

      Natural gas heating is pretty damn efficient – so you don’t get much savings there. Maybe 0.5-1 pWh.

      There is already around 300 tWh of hydro installed in the U.S, and around 800 tWh of nuclear. So that helps a bit.

      So the problem is a little less bad then I let on before… 109,393 sq-miles instead of 151,000. I still think this would be an envioronmental disaster to use that much land for solar/wind, not to mention the unbelievable amount of rare earth metals it would require ( https://motherboard.vice.com/en_us/article/a3mavb/we-dont-mine-enough-rare-earth-metals-to-replace-fossil-fuels-with-renewable-energy ). I don’t think there is very much hydro resource to develop in the U.S. – so that leaves Nuclear (and realistically a little natural gas for flexability) to fill in the base load generation in my opinion.

    3. Great points all around. A few more thoughts…

      Heating, particularly industrial heating, strikes me as one of the largest challenges in transitioning away from fossil fuels.

      I think we’ll see electric vehicle charging become more and more local with community scale solar reducing the need for long haul transmission (and the associated energy losses from natural gas, distribution, etc). The fact that cars are idle most of the time, especially during the strong mid-day sun, means solar charging can be very flexible, somewhat mitigating the intermittency challenges. This isn’t a panacea but I think it’ll help a lot.

      Your point about hydro is spot on but one expert I interviewed reminded me that there are 73,000-ish dams in the US, the vast majority of which don’t have hydro. Collectively, these dams could add microhydro facilities and hydro could once again see its contribution rising.

      I too struggle to with how much land might be needed but given how much is already used for oil and gas leases as well as growing corn for ethanol (an economically and environmentally debatable practice), it’s arguable that the land could be put to better use.

      Lastly, on the rare earth materials, my research leaves me increasingly encouraged that running out of this stuff is less an issue than I had thought. I touched on this a little bit in my recent article: https://www.freeingenergy.com/why-does-the-cost-of-renewable-energy-continue-to-get-cheaper-and-cheaper/

    4. I believe Jared is making a valid calculation. We need to consider all energy uses if the plan is convert all industry, transportation, residences, etc. to renewable electric energy. I checked his numbers and they look accurate according to the link given which is to the EIA (Energy Information Agency). So to initiate the Green New Deal, to convert everything to solar would require at minimum 151,500 square miles of panels not including batteries. So for the panels we need at minimum 400 miles by 400 miles. For batteries, assuming Musk is right, 4 miles by 4 miles. Still doable. I yes, panels can go on roofs. I’m ignoring the recalculation below because the population if growing and if look to the future, more energy will be required.
      Jareds statement, “I still think this would be an environmental disaster to use that much land for solar/wind,..” is something to think about. The number is a little less than the entire State of California. How much land and water and air has been polluted and destroyed by mountain top removal, strip mines, coal mines, oil drilling, fracking, ??? But still we can’t cover that much land with panels or even anything close to it. Even half of that. So, with that in mind, I think the only solution besides returning to pre Industrial Revolution lifestyle, is to develop nuclear power plants that 1) will never meltdown, and 2) do not produce ridiculous amounts of radioactive wastes, and better, use the waste materials from the nuclear plants currently operating as fuel. We need a Manhattan Nuclear Power Plant Redesign Project. Note that such designs do exist but need work. For example; Lead Cooled Fast Reactor. See Wikipedia.

    5. the 20K square miles was off by a factor of 2 and way out-of-date.

      It was covered in the Article above.

      More realistic numbers are 10K square miles — but that is dropping all the time.

      =========
      But far worse, trying to mix in “Energy Equivalent” units between sources turns your numbers into total nonsense — sorry.

      The supposed “Embodied Energy” or such of Oil (especially) and Gas (some what less) are So Lossy when put into use — that your likely numbers beyond the simple Electricity equations are likely to be off by as much as a factor of 10X.

    6. I’m aware embodied energy =/= energy produced; that’s why I included a thermal efficiency of ~25% for ICE cars and ~60% for power plants. Because that represents how much of the embodied energy gets extracted.

    7. Even with 25% as the through put from fuel tank to wheels, it ignores the losses before retailing. The overall path from “Well-to-Wheels” (which would be the “embodied energy” on the front end to what it actually produces on the final end) is more likely down around 10%. Dunno if you follow how much internal process energy it takes to refine Oil?

      But when the numbers are getting that wild — a better path than trying to guess “equivalents” is to just add up the actual path from Solar Cells to Wheels — if that is what one is actually trying to model. Those numbers are now pretty well known. Sampling Tesla(s) and Chevy Volts/Bolts — you can reasonably allow 250 Watt-hours per mile, with the 3.22 Trillion Miles driven. That is what the complete Solar Cell to Wheels model actually looks like — without having to hearken back to any existing equivalents.

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