As of now, Google has contracts to purchase three gigawatts of output from solar and wind farms around the world. As part of its green energy efforts, the company has also started publishing an environmental report on its progress and has a website that details its ongoing work.

However, last year, Greenpeace gave Google a D+ in its Guide to Greener Electronics, doling out low marks for Google's lack of transparency in regards to its supply chain footprint (as opposed to its operations footprint) and for purchasing renewable energy in regions outside of where it actually consumes electricity. But Greenpeace did give Google an A for its advocacy efforts. Google was an outspoken proponent of staying in the Paris climate agreement and in 2016, it along with Apple, Amazon and Microsoft backed the EPA's Clean Power Plan.

Google said today that while achieving 100 percent renewable energy offset was an important milestone, it's just the beginning. "We do want to get to a point where renewables and other carbon-free energy sources actually power our operations every hour of every day," it said. "It will take a combination of technology, policy and new deal structures to get there, but we're excited for the challenge. We can't wait to get back to work."