Both gas-fired and coal-fired generation ceded market share to renewable resources in 2017 as thermal generation's overall share of U.S. generation slipped from 83.9% to 81.7%.
According to the U.S. Energy Information Administration's latest "Electric Power Monthly" released Feb. 27, utility-scale generation declined 1.6% to 4.02 billion MWh, with coal supplying 30.0% of the nation's power and natural gas at a 31.7% share. During the year, renewable generation supplied 17.1% of the nation's power, compared with 14.9% a year earlier.
Coal-fired generation declined 2.6% year over year to 1.21 billion MWh, while gas-fired generation declined 7.8% to 1.27 billion MWh. Meanwhile, renewable generation grew 12.8% to 687.3 million MWh.
In December 2017, utility-scale generation net of hydroelectric pumped storage increased 0.2% year over year to 346.6 million MWh.
Over the same period, gas-fired generation climbed 10.1% to 106.1 million MWh, accounting for 30.6% of the net total. Meanwhile, coal-fired generation declined 10.3% versus the prior-year period to 106.6 million MWh, to account for 30.8% of the nation's electricity.
Renewable output climbed 0.8% year over year to 55.4 million MWh as growth among renewable resources was mixed.

Power-sector coal stockpiles fell by 6.1 million tons during the month, above the 10-year average draw of 2.7 million tons. During the prior 10 years, December stockpile fluctuations versus the prior month have ranged from a draw of 14.3 million tons to a build of 9.0 million tons.
The EIA estimates that the December 2017 stockpile level of 137.2 million tons translates to 87 days of burn and 94 days of burn, respectively, for bituminous and sub-bituminous coal, which is 4.1% and 26.3% above the five-year averages for the month.

