Katie Fehrenbacher, Gigaom, has good overview on Apple’s use of clean power for data centers. Katie has been covering this story for a while, and was one of the few to get a tour of Apple's data center in North Carolina (back in 2013):
Now, the official embrace of these internet companies and clean power is just one part of the story. There’s a whole host of smaller data center operators that can’t afford to deal at the scale of Google or Apple. But Google and Apple are still paving the way for the smaller companies by changing utilities minds that there’s a good business to be had in clean power.