The energy from the NextEra Energy Resources wind farm will be sufficient to power "several data centers," Google wrote on its blog.
In 2007, Google announced its intention to become carbon neutral by the end of the year.
The deal is the first for Google Energy, a subsidiary of the company that received federal approval to trade energy on the open market.
In addition to wind power, Google has also taken advantage of corporate solar installations at its Mountain View headquarters.
Google announced the energy deal on its company blog, explaining:
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. 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.