UPDATE 1-NRG Yield to buy largest U.S. wind farm for $870 mln

(Updates sourcing)

June 4 (Reuters) - NRG Yield Inc, a unit of NRG Energy Inc, said it would buy California's Alta Wind Energy Center, the largest wind farm in North America, for $870 million.

The acquisition totals 947 megawatts of operating wind capacity and includes a portfolio of land leases associated with the Alta Wind facility, NRG Yield said on Wednesday.

The deal is expected to increase NRG Yield's annual run-rate earnings before interest, taxes, depreciation and amortization (EBITDA) by about $220 million.

Alta Wind, located in the Tehachapi Pass in California's Kern County, is owned by Terra-Gen Power LLC, an affiliate of private-equity firms Global Infrastructure Partners and Arclight Capital Partners.

In December 2013, NRG Energy said it would close down two of its coal-fired power plants in Maryland due to tightening air emission regulations.

(Reporting By Sneha Banerjee, Narottam Medhora and Ankush Sharma in Bangalore; Editing by Gopakumar Warrier and Simon Jennings)