From a worthwhile discussion of the issues, here:
America produces 40 percent of its electricity from coal. Eight states, including Kentucky, Indiana, Ohio, Missouri, and West Virginia, use coal to generate more than 80 percent of their electricity. But over 100 coal-fired generating plants have closed since January 2010, mostly due to Environmental Protection Agency regulations.
EPA's Mercury and Air Toxic Standards for Power Plants rule, issued last December, will make electricity generation more complex and expensive, especially in the eastern half of the United States. It will lead to the closure of many coal- and oil-fired power plants that would be too expensive to bring into compliance. Ultimately, power users will bear these costs.
