It appears inevitable, absent legislative intervention, that regulation under the Clean Air Act (CAA) will move beyond mobile sources to the industrial and power facilities that emit most U.S.greenhouse gas (GHG) emissions. We analyze the mechanisms available to the EPA for regulating such sources, and identify one, New Source Performance Standards (NSPS) as the most predictable, likely, andpractical, i.e. knowable, pathway. Based on the legal structure of the NSPS and the EPA’s traditional approach, we analyze a hypothetical GHG NSPS for one sector, coal electricity generation. This analysis indicates that efficiency improvements and perhaps biomass cofiring could be implemented through the NSPS, yielding modest but meaningful emissions reductions. Trading could also rein in costs. Though analysis is limited to one sector and does not include modeling of costs, it suggests that CAA regulation, though inferior to comprehensive climate legislation, could be a useful tool for regulating stationarysource GHGs.