After spending several years and a lot of cash (more that $3 billion so far), Google is almost at the point where it is able to use only renewable energy for everything, including server farms and office spaces. Google has worked hard at making it's server hardware very efficient - around 50% more efficient that traditional equipment, and this has helped to get it to the place when practically everything can run on renewables.
“We were one of the first corporations to create large-scale, long-term contracts to buy renewable energy directly; we signed our first agreement to purchase all the electricity from a 114-megawatt wind farm in Iowa, in 2010. Today, we are the world’s largest corporate buyer of renewable power, with commitments reaching 2.6 gigawatts (2,600 megawatts) of wind and solar energy. That’s bigger than many large utilities and more than twice as much as the 1.21 gigawatts it took to send Marty McFly back to the future,” Google announced.Great Scot!