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:
- The efficiency of the PV system (because that defines the area needed)
- The fraction of land the modules cover within the deployed system (packing factor)
- 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.