French utility EDF, the world's biggest operator of nuclear plants, is pulling out of nuclear energy in the United States, bowing to the realities of a market that has been transformed by cheap shale gas. Several nuclear reactors in the US have been closed or are being shuttered as utilities baulk at the big investments needed to extend their lifetimes now that nuclear power has been so decisively undercut by electricity generated from shale gas. The spectacular fall of the price of gas in the US, which was unimaginable a few years ago, has made this form of energy ultra competitive vis a vis all other forms of energy," EDF Chief Executive Henri Proglio told a news conference. EDF agreed with its partner Exelon on an exit from their Constellation Energy Nuclear Group (CENG) joint venture, which operates five nuclear plants in the United States with a total capacity of 3.9 gigawatts. "Circumstances for the development of nuclear in the US are not favourable at the moment," Proglio said. International Energy Agency analyst Dennis Volk said CENG's eastern US power plants were located in some of the most competitive power markets in the country, with high price competition, growing wind capacity and cheap gas. "It is simply not easy to invest in nuclear and recover your money there," Volk said. Proglio said EDF would now focus on renewable energy in the United States. EDF employs 860 people in US solar and wind, and since 2010 its generating capacity has doubled to 2.3 gigawatts.