NRG Energy Inc. has successfully converted four of its coal-fired facilities to run on natural gas, slashing the power plants' combined carbon footprint by more than 80%. The modified units can collectively produce 2,780 MW, enough to power more than 2 million average homes, according to a Dec. 19 news release.

The changes were made as part of its fleet optimization strategy announced in early 2015. At the Big Cajun 2 generating station in New Roads, La., a 540-MW unit was converted. At the Joliet generating station in Illinois, three units totaling 1,326 MW were converted. At the Shawville generating station in Pennsylvania, four units totaling 590 MW were modified and are in final commissioning. At the New Castle generating station, also in Pennsylvania, its three units totaling 325 MW were modified.

"Driven by the economics of power generation, we modified units at four plants to switch from burning coal to natural gas, significantly reducing greenhouse gas and other emissions, while maintaining reliability in the system. Along with growing our renewables portfolio, these optimization projects keep NRG competitive while advancing on our sustainability commitments," NRG Energy CEO Mauricio Gutierrez said in a statement.

In November, NRG also announced that it will convert its mothballed Dunkirk coal-fired power plant in New York to natural gas after Entergy Corp. dropped a lawsuit against the New York State Public Service Commission for backing the $204 million subsidized repowering plan.