The Union of Concerned Scientists has gone through the catalog of America’s coal plants, and found hundreds of mostly small, old, polluting, inefficient generating units that just aren’t worth operating any more, even on a purely economic basis. They looked at several different sets of assumptions, including different natural gas prices going forward, a price on carbon, whether or not the competing natural gas fired generation would need to built new, or whether it existed already with its capital costs paid off, and whether or not the production tax credit for wind ends up being renewed. In all of the scenarios considered, they found substantial coal fired generation that should be shut down on purely economic grounds, above and beyond the 288 generating units that are already slated for retirement in the next few years. They also found that some companies — especially those in traditionally regulated monopoly utility markets in the Southeast — are particularly reluctant to retire uneconomic plants, perhaps because they can effectively pass on their costs to ratepayers, who remain none the wiser.