A combination of lower natural gas prices and increased political pressure has led electric utilities throughout the country to favor natural gas over coal, which produces far more toxic and greenhouse gas emissions but historically has been much less expensive.
But the trend is not as bad as it looks for the coal industry.
And it might not be as good as it looks for the environment.
Monthly coal- and natural gas-fired power generation were nearly equal in April 2012, marking the first time coal had given up its dominance.
Modestly higher natural gas prices over the past year have returned the balance to coal, but the colorless, odorless gas continues to gain market share, both because of economics and because of growing political pressure against coal.
Public Service Co. of Oklahoma earlier this year agreed to phase out its last coal plants by 2026. Regulators throughout the country are looking more closely at coal-fired power plants, which release relatively high amounts of carbon dioxide, sulfur and other pollutants into the atmosphere.
In part because of the changes, the country's carbon emissions have dropped steadily over the past four years.
A comprehensive survey of U.S. energy trends by Bloomberg New Energy Finance in February found that the country's carbon emissions are at their lowest point in nearly 20 years, down almost 13 percent from their peek in 2008.