The U.S. Environmental Protection Agency’s (EPA’s) Clean Power Plan was accompanied by model rules for states that provide both a mass-based and a rate-based approach. The model rules, once finalized, will give states a streamlined but customizable template that is trading ready. EPA also provided proposed mass- and rate-based federal plans that would be implemented absent state-promulgated plans. They are similar to the proposed model rules, but they exclude certain compliance options, such as demand-side energy efficiency under the rate-based approach. This Article explores the details and important aspects of these various compliance approaches.