How much space would it take to put the whole of the United States on solar power. Well, it depends a lot on the region where you install those solar panels. Las Vegas gets almost twice as much solar energy as some other places, with 26.8 kilowatt-hours per day in a five-kilowatt system, compared to 14.9 kWh per day in Seattle. The figure that’s been bandied about is that it would “only” take 17,500 square miles to generate the 4 trillion kilowatt-hours of energy we burn through every year.