Since 2017, Google pledged to power its data centres and offices with 100 percent renewable energy.

Now the tech company said it's surpassed that, announcing in a blog post that it purchased more power from solar and wind than was used by its operations globally last year. Google said it's the first company of its size to reach that goal.

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Of course, Google isn't completely powered by solar and wind.

For every kilowatt hour of electricity the company consumes, it purchases a kilowatt hour of renewable energy to replace it, which is sourced from a wind or solar farm built specifically for its needs.

Google said it has contracts to purchase three gigawatts (3GW) of output, but that it's not yet possible to power itself fully with renewable energy. The company hopes that one day it reaches that goal, but said its initiatives helped to spur new wind and solar developments.

"What’s important to us is that we are adding new clean energy sources to the electrical system, and that we’re buying that renewable energy in the same amount as what we’re consuming, globally and on an annual basis," Urs Hölzle, Google's SVP for technical infrastructure, said in the post.

In 2015, only 44 percent of Google's energy needs came from renewables. That improved to 57 percent by 2016, before it covered all its needs come 2017.

As Google leaps ahead, other tech companies have also pledged to become powered by green energy.

Apple Park is entirely run by renewables, as are many of its facilities around the world. Amazon is working to build dozens of wind farms, and its U.S. fulfilment centres are powered mostly by solar. Facebook aims to have 50 percent clean and renewable power in its energy mix this year.