The $2bn project was among the earliest and largest recipients of a loan guarantee from a controversial US Energy Department (DOE) programme.

Shepherds Flat is now the second-largest US wind farm behind the 1.02GW Alta Wind Energy Center in California, with the 781MW Roscoe Wind Farm in Texas in third place.

Utility Southern California Edison has signed three 20-year agreements to purchase all power from the project, which is spread over 77sq km.

Shepherds