Land Needed To Make All Our Electricity with Solar Photovoltaics
A number that comes up frequently is the “what is the percentage of US land needed to make all our electricity with PV?”
The answer is about 0.7%: approximately a square 160 miles on a side (or 25,700 square miles); or 260 km on a side (66,800 km2).
The assumptions needed to calculate this are:
1. The efficiency of the PV system (because that defines the area needed)
2. The fraction of land the modules cover within the deployed system (packing factor)
3. The output in kWh per installed W, which depends on the sunlight, tracking or not, and other losses within the system.
These numbers can vary quite a bit. For example, system efficiencies are between 5% and perhaps 15% at this time, and as they evolve, will almost certainly rise. Traditionally one is safe to choose 10% as the system efficiency, knowing full well it is likely to be better.
Packing factor varies between tracking and nontracking systems, and seems to be about three for those where land is a constraint. I assume simple, nontracking systems.
Output (kWh/W installed) depends strongly on sunlight and tracking. Assuming nontracking systems but mostly in sunny places allows one to estimate about 1.8 kWh per installed W output per year.
Calculations Showing Land Area
|m2/MW modules (10% System Efficiency)||10,000|
|Area of US (km2)||9372610|
|US electricity use TWh/yr||4000|
|% US land for All US Electricity from PV||0.7% (66,800 km2)
So, with these assumptions it would take less than 1% of US land area to make all our electricity with PV. If we put more in the sunniest places, it would take less; if we put more all around the country, more. These numbers should be about right as we evolve, but probably conservative – that is, real land area will be a little lower.
By the way, hydro produces 7% of our electricity and uses 100,000 km2 for lakes behind the dams. This is about 1% of US land area. So in comparison, hydro is about 20 times more land intensive per kWh than PV ((1%/7%) / (0.7%/100%)). This is actually a more important answer than the raw number, since it puts it in perspective. PV land area is 20 times less than hydro land area, yet we value hydro a great deal. And PV use doesn’t make any permanent alteration on the land like making artificial lakes.