Google's signed a 20-year deal to buy power from an Iowa wind farm as part of its plan to become carbon neutral.
From the end of the month, the company will start buying 114MW-worth of wind generation at the NextEra Energy Resources Story County II facility.
It won't use the energy directly to power its server centers - the logistics are just too tricky, it says - but will instead sell it back to the grid as a way of offsetting its own power consumption.
"By contracting to purchase so much energy for so long, we’re giving the developer of the wind farm financial certainty to build additional clean energy projects," says senior VP for operations Urs Hoelzle.
"The inability of renewable energy developers to obtain financing has been a significant inhibitor to the expansion of renewable energy. We’ve been excited about this deal because taking 114 megawatts of wind power off the market for so long means producers have the incentive and means to build more renewable energy capacity for other customers."
Google announced in 2007 ago that it would become carbon neutral by the end of that year - a tall order for a company which uses so many data centers.
Since then, it says, it's introduced one of the largest corporate solar installations in the world, purchased carbon offsets and built some of the world's most efficient data centers. It bought a stake in two wind farms back in May.
But the deal also has financial advantages for the company. Buy signing a long-term, fixed price purchase agreement, it says, it's partially protecting itself against future price increases - "a case where buying green makes business sense," it says.