In what the company called a “landmark moment,” Google has announced that all of its data centers and offices will be powered 100% by renewable energy starting next year.

As Adam Vaughn reports for The Guardian, Google is already the world’s biggest corporate buyer of renewable energy, having purchased 44% of its power from wind and solar farms last year. The 100% target, set in 2012, has taken five years to achieve because of complexity involved with negotiating power purchase agreements, Vaughn explains. “It’s complicated, it’s not for everyone: smaller companies will struggle with the documents. We are buying power in a lot of different jurisdictions, so you can’t just copy and paste agreements,” said Marc Oman, EU energy lead at Google.

“We are convinced this is good for business, this is not about greenwashing. This is about locking in prices for us in the long term. Increasingly, renewable energy is the lowest cost option,” Oman told The Guardian. “Our founders are convinced climate change is a real, immediate threat, so we have to do our part.”