Google’s total energy use: 260 megawatts.
That’s about a quarter of the output from a large nuclear reactor. For all they do, it doesn’t seem like all that much.
It would be cool of them to build enough renewable energy generation and storage capacity to serve their own purposes, however. It would be quite feasible, with modern wind turbines capable of generating about two megawatts each. They could use a combination of wind, concentrating solar, solar photovoltaic, geothermal, and so on. They could balance supply and demand using options like pumped hydroelectric storage, demand management, and multi-lagoon tidal systems.
The linked article shows that Google is already on their way to being renewably powered:
“In part because of special arrangements the company has made to buy electricity from wind farms, Google says that 25 percent of its energy was supplied by renewable fuels in 2010, and estimates that figure will reach 30 percent in 2011. “