842 megawatts is ... more than enough to power all the homes in the Denver metro area. It's also enough to keep about 15 percent of Google's data centers humming. On Thursday, Google announced that it had finalized contracts to buy 842 megawatts of wind and solar energy from plants in the US, Chile, and Sweden, nearly doubling the company's total clean energy capacity. The contracts ... help to give the energy companies financial stability to be able to build additional clean energy facilities. Renewable energy now provides about 37 percent of the total energy consumed by Google's data centers worldwide. This purchase is the largest of its kind ever made by a non-utility company, but Google isn't the only tech giant shifting over to clean energy. One of Facebook's five data centers is powered entirely by a nearby wind farm, and the company says it plans to get 50 percent of its energy from renewable sources by 2018. Amazon's cloud computing division announced last year that its operations would eventually be powered completely by clean energy. And in 2014, Apple announced that all of its offices, stores, and data centers in the US were being powered ... renewable sources. Google was one of 13 large companies that collectively invested more than $140 billion in new clean energy projects in July as part of the American Business Act on Climate Pledge. Apple and Microsoft were also part of the pledge; both companies said their operations would eventually be 100 percent powered by renewable energy.