On August 3, 2015, President Obama and the U.S. Environmental Protection Agency (EPA) released the long-awaited final Clean Power Plan (CPP). A plan with greater legal defensibility and a longer implementation timeframe than the original proposal, some of the uncertainty surrounding compliance options has been alleviated. At a workshop for the National Association of State Energy Officials (NASEO), Ken Colburn looked at the implications, opportunities, and challenges of the final CPP. The final CPP still affords state regulators broad latitude in crafting a compliance plan. While energy efficiency (EE) was removed from the four “building blocks” for compliance in the final rule, many states will implement it as an effective, least-cost approach for meeting some or all of the required greenhouse gas emission reductions. EE supports a multi-pollutant approach that has positive effects on air quality—such as helping meet the new National Ambient Air Quality Standards (NAAQS)—in addition to facilitating CPP compliance.