In rural Grady County, Oklahoma, a large wind farm–generating as much power as around 30,000 homes use–probably wouldn’t exist without Google. The same is true for a sprawling solar farm in the desert in Chile, and a wind farm now under construction in Norway.

In each project, and a total of 20 wind and solar projects around the world, Google made long-term commitments to buy the power produced (in some cases, all of it), enabling developers to get funding to add new renewable power to the grid. The commitment totals 2.6 gigawatts of energy, making Google the world’s largest corporate buyer of renewable energy.

The company says that in 2017, it will buy enough renewables to account for its entire electricity use (though its data centers are still also plugged into the grid, where they use coal and natural gas power, as well). That’s a big deal; in 2015, to run the data centers that let you check email and watch YouTube, and to power its own offices, Google consumed nearly as much energy as the city of San Francisco did over the year.

Other companies, such as Apple, are also close to a “100% renewable” goal of buying as much renewable electricity as the power they use. But because Google uses so much more electricity, it’s also buying more renewables.

Google signed its first power purchase agreement, a long-term contract to buy from a wind farm in Iowa, in 2010. That farm produces 114 megawatts of power; now the company is committed to buying nearly 23 times more renewable energy than that.

“The significant reduction in price of renewables is one of the reasons that we’ve been able to really scale this program,” says Gary Demasi, director of operations for Google’s data center energy and location strategy. Over the last six years, the cost of wind power dropped 60%; solar power became 80% cheaper.

“Frankly, one of the reasons why we do this is because it makes business sense from a cost perspective,” he says. Data centers use an enormous amount of energy, and the cost of natural gas and coal fluctuates over time; the cost of solar and wind can be locked into a long-term contract and give predictability as the company makes financial plans.