As recently as 2008, coal's generation market share was 48%. Then it collapsed to 37% in 2012, as a glut of natural gas crashed the gas price and caused a large move from coal generation to natural gas.
Since its 2012 low, coal rebounded to 39% in 2013. And 2014 looks like another year of market share gains for coal, with its market share going above 40% for the first time since 2011. EIA states:
"Natural-gas-fired generation accounts for a 27.0% share of total generation during 2014, down from 27.5% in 2013 as a result of rising natural gas prices. In contrast, the share of generation fueled by coal increases from 39.0% in 2013 to 40.3% in 2014. Renewable energy sources, including hydropower, account for 12.9% of total generation this year, the same as in 2013."
EIA projects no total increase in renewable energy generation, despite big gains for wind and solar, because major droughts will cut hydro production.
Rising natural gas prices are good for coal, as coal and natural gas continue to be locked in a fierce almost daily battle for generation market share. One consequence of the rising market share for coal generation in 2014 is another year of increasing carbon emissions. This year will likely be the second year in a row of rising coal generation market share and increasing US carbon emissions.
As for coal's prospects in 2015, EIA forecasts a loss of market share, with more coal plants closing next year. That forecast's accuracy, however, depends heavily on natural gas prices in 2015. Stay tuned.