Rockstar
What will be the largest wind turbine on earth is currently being installed in Emden, Germany by Enercon.

The E-126 is a more sophisticated version of the E-112, formerly the world's largest wind turbine and rated at 6 megawatts. E-126, a rotor blade length of 126 meters (413 feet), is officially rated at 6 megawatts too, but will most likely produce 7+ megawatts (or 20 million kilowatt hours per year). That's enough to power about 5,000 households of four in Europe, or about 1776 American homes on one wind turbine.

These turbines are equipped with a number of new features: an optimized blade design with a spoiler extending down to the hub, and a pre-cast concrete base. Due to the elevated hub height and the new blade profile, the performance of the E-126 is expected to by far surpass that of the E-112.