This element of Obama's impending energy policy hasn't gotten nearly the attention it deserves. If he does it right, it could be the secret weapon that kills new coal plants for good — with far greater certainty than a middling cap-and-trade program. Obama has always said, to those who were listening closely, that he plans to prevent the construction of a new fleet of dirty coal plants, if not by carbon pricing then by other means. EPA regs are the other means. Beyond that, and perhaps even more importantly, EPA regs could hasten the demise of existing coal plants.
Read the whole thing for a more detailed understanding of what EPA may end up doing. And for the wonks among you, David also has a more detailed explanation than I did of the difficulties with using the machinery of the Clean Air Act to regulate greenhouse gases.
New coal plants are already expensive and hard to build. If EPA institutes even modest new CO2 regs they'll become so prohibitively expensive that we'll never build another one on U.S. soil. Politically, this will cause (a) howls of protest from the midwest, which relies heavily on coal-fired electricity, and (b) enormous pressure to set up an alternative regulatory regime. But any plausible alternative, even if it's weaker than the EPA regs, is likely to raise the price of building a coal-fired power plant beyond what anyone is willing to pay for it. There's a pretty good chance that this is, finally, the beginning of the end for coal.