Under the proposed Clean Power Plan (CPP), traditional air regulation based on solutions at individual generation plants will shift to a more flexible approach based on four building blocks, one of which is energy efficiency. Given most states’ experience with efficiency policies and programs, this could be a commonly proposed element of state CPP compliance plans. This paper focuses on tracking ownership of emissions reductions to help regulators understand how states can incorporate energy efficiency into their compliance plans. This tracking can be easily accomplished using the existing infrastructure that states and regions have already developed for renewable energy certificates (RECs). The paper also considers the implications of a new tradable instrument that EPA might use to comply with the CPP, and explores the questions of how such an instrument might be issued and tracked and whether existing systems could accommodate it.