Happy Hereford, which is the name of the wind farm, produces an output of 240 MW. The purchase of Happy Hereford, which is Google's fifth step towards their eco-friendly goal, brings the amount of wind-generated power they've purchased to 570 MW, which they claim could power 17,000 average US households. The wind farm should begin generating energy by late 2014.
Once Google completes the purchases, they'll sell the energy to the wholesale market, retire the credits, and use any remaining credits to lower their carbon footprint in another location. The company has already done similar things in both Oklahoma and Iowa.