The current downward trend in coal - fired generation began in 2007, when increased U.S. production of natural gas (particularly from shale) led to a sustained downward shift in natural gas spot prices and increased generation from natural gas - fired generators. (eia.gov)
Natural gas spot prices in 2015 at the Henry Hub in Louisiana, a national benchmark, averaged $ 2.61 per million British thermal unit (MMBtu), the lowest annual average level since 1999. (eia.gov)
Several factors are likely contributing to increased natural gas spot trading in the Marcellus area: (eia.gov)