Electricity Generation From Coal, Decline's

Amid historically low natural gas prices and the warmest March ever recorded in much of the United States, coal’s share of total net generation dropped to 34%—the lowest level since at least January 1973.
Natural gas prices were near 10-year lows this winter, leading the generators in some states (such as Ohio and Pennsylvania) to increase their dispatch of natural gas-fired plants. Newer vintage natural gas-fired units operate at higher efficiency than older, fossil-fired units, which increases the competitiveness of natural gas relative to coal.

Source: coals-share-of-electricity-generation-continues-to-decline