Google’s total purchase of energy from renewable sources in 2017 was greater than the electricity used by its global operations, the tech giant has said. This follows on from a 2016 announcement that the business was on target to buy enough renewable energy to “match” electricity usage.

In a blog post Wednesday, Google’s Senior Vice President for Technical Infrastructure, Urs Hölzle, described what the business meant by “matching.” Put simply, for every kilowatt hour of electricity the company used in 2017, it bought a kilowatt hour of renewable energy from a solar or wind farm built specifically for Google, according to CNBC.

Hölzle said that Google now had contracts to buy 3 gigawatts of output from renewable energy projects, and that no corporate purchaser was buying more renewable energy than Google. Renewable energy contracts for Google had resulted in more than $3 billion in new capital investment across the globe, he said.

“We say that we “matched” our energy usage because it’s not yet possible to “power” a company of our scale by 100 percent renewable energy,” Hölzle explained.

“It’s true that for every kilowatt-hour of energy we consume, we add a matching kilowatt-hour of renewable energy to a power grid somewhere,” he added. “But that renewable energy may be produced in a different place, or at a different time, from where we’re running our data centers and offices.”