Renewables provided 55 percent of all new electrical capacity worldwide last year, the most ever. In some regions, solar is the cheapest source of power, and it will only get cheaper. Bloomberg New Energy Finance estimates that a watt of power from ground-mounted solar will drop a further 36 percent by 2025. Solar's appeal isn't just one of cost. It's the most democratized and decentralized power source. Solar systems sometimes feature a single panel; others line hundreds of acres of desert.