The company says its network of data centers will use renewable energy for 50 percent of its needs by the end of 2018, among other sustainability pledges.

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Microsoft has pledged to make its cloud a bit greener.

Efficient energy use was easier for Microsoft when it was a builder of out-of-the-box software whose main energy need was keeping the lights on at its office parks.

But with the company joining in the race to build the giant, power-hungry data centers that underpin cloud computing, that’s becoming a more complicated task.

Such data centers across the industry “will rank by the middle of the next decade among the large users of electrical power on the planet,” Microsoft president Brad Smith said Thursday in comments timed to a conference of renewable-energy buyers held at the company’s Redmond campus. “We need to keep working on a sustained basis to build and operate greener data centers that will serve the world well.”

According to environmental watchdog Greenpeace, both Microsoft and Amazon are building data centers faster than they can turn them green.

About 44 percent of the power behind Microsoft’s network of data centers was generated by wind, solar, or hydroelectric power, Smith said Thursday. He said Microsoft was committed to raising that portion to 50 percent by 2018, and 60 percent “early in the next decade.”

Amazon chief executive Jeff Bezos said at his company’s shareholders meeting this week that it was on track to have renewable-energy sources behind 40 percent of its data-center consumption by the end of the year, with a goal of reaching 100 percent by an unspecified date.

Smith outlined some of Microsoft’s other commitments to sustainability on Thursday, including a pledge of public transparency in its energy use, further investment in new energy technologies, and advocacy for pro-renewable-energy public policy.

Microsoft spends about $20 million a year offsetting its carbon emissions, from air travel to energy use. As part of that effort, the company bought a bundle of credits tied to a 520-acre forest near Mount Rainier.

Smith on Thursday said Microsoft would retire all credits or other certificates for green-energy purchases, rather than selling them down the line.