This brief looks at the costs of implementing the EPA’s Clean Power Plan. Specifically, it examines whether implementing the CPP on a state-by-state basis—that is, with each state meeting its own individual target for emissions reduction by 2030, rather than establishing regional targets—is economically efficient. The economic analysis uses data from electricity-generating firms participating in the Pennsylvania-New Jersey-Maryland (PJM) Interconnection to examine the relative economic efficiency of regional versus state-by-state implementation of the CPP. The research indicates that state-by-state implementation would yield the lowest electricity prices in 2030.