This short TED video gives some interesting statistics about how much land it will take to power the world – which is 3 terawatts. They don’t give any info on who or where this information came from. I think some of it isn’t accurate.
The United States generates about 1.2 terawatts of power.
https://www.ted.com/talks/ted_ed_how_much_land_does_it_take_to_power_the_world