“Coal-fired power plants, many of which are aging toward retirement, generated nearly half of the nation’s electricity in 2007. Today, they produce 30 percent and, for the first time, are being out-produced by newer power plants whose generators run on natural gas. In 2016, natural gas generated 34 percent of U.S. electricity, up from 22 percent 10 years earlier, according to U.S. Energy Information Administration data. . . .
“Coal no longer enjoys a substantial price advantage over its chief competitor, due to the efficient harvesting of shale gas with hydraulic fracturing technology that has roiled energy markets. . .
“But coal is not the only energy industry under pressure. Following a trend seen in other states, Exelon in May announced plans to close its Three Mile Island nuclear plant near Harrisburg. Reasons include difficulties selling guaranteed power for coming years and competing with cheaper natural gas.”