of generating 316 MW of electricity. The Frederickson Generating Station in Pierce County is a simple-cycle natural gas-fired plant capable of generating 147 MW of electricity. The Frederickson 1 Generating Station in Pierce County is a combined-cycle natural gas-fired plant capable of generating 275 MW of electricity. PSE owns a 50% share, or 137 MW. The Whitehorn Generating Station in Whatcom County is a simple-cycle natural gas-fired plant capable of generating 147 MW of electricity. Wind power and other generation sources, such as biomass and landfill gas, account for 1% of the utility's electricity fuel mix. PSE owns and operates these wind-power facilities: The Hopkins Ridge Wind Facility in southeast Washington's Columbia County began commercial production in 2005. Hopkins Ridge's 87 wind turbines have the capacity to generate 157 MW of electricity. The Wild Horse Wind and Solar Facility in central Washington's Kittitas County began production in 2006 and was expanded to include 22 turbines in 2009. Wild Horse's 149 wind turbines have the capacity to generate 273 MW of electricity. In 2012, the first phase of the Lower Snake River Wind Project began in Southeast Washington's Garfield County. Lower Snaker River Phase 1's 149 turbines have the capacity to generate 343 MW of electricity. Coal-fired power is a major contributor to PSe's fuel mix at 36% of PSE's 2018 electricity generation sources, the largest share in 2018. The company owns a stake of the Colstrip Unit 3 coal power plant in eastern Montana. A net metering program allows residential and business customers to return extra renewable energy solar power to the grid. An additional approximately 1% per year of generation comes from—or actually is reduced by—state mandated I-937 energy efficiency programs, adding an average 25 additional "Negawatts" generation capacity per year. For its natural gas service to customers, PSE purchases a portfolio of natural gas supplies originating in western Canada and the U.S. Rocky Mountain states. History PSE was formed in 1997 when two of its largest ancestral companies – Puget Sound Power & Light Company and Washington Energy Company – merged. In 2009 Puget Sound Energy was sold to foreign investors led by Macquarie Group, in a leveraged private equity buyout. Puget Holdings, the U.S. title of this group of long-term infrastructure investors, merged with Puget Energy, PSE's parent company to form the current business structure. Puget Energy is a holding company incorporated in the State of Washington.