This summer, an electrical power auction in Chile attracted successful bids by wind generators willing to provide electricity at $0.04 per kilowatt hour and solar generators at $0.03 per kwh, easily beating fossil-fuel competitors. That success reflects cost reductions over the last six years, with the cost of solar power falling about 70 percent and wind power costs down more than 30 percent. Further reductions are inevitable.
Of course, the sun doesn't always shine, and the wind doesn't always blow, but intermittency problems are increasingly solvable as the cost of battery and other energy storage falls, and as smart meters and control systems make it possible to shift the timing of some electricity demand. It is now certain that, within 20 years, many countries could get most of their electricity from renewable sources at an easily affordable price.
To be sure, solar and wind farms require large land areas. But at the global level, there is plenty of space.