The Clean Power Plan (CPP) – the first national carbon regulation in the US was promulgated on Aug 3, 2015. The plan aims to reduce carbon emissions to 32 percent below 2005 levels by 2030. While the ultimate goal is clear, the rule provides for multiple pathways to get there. As such, there are more than 560 trillion theoretical outcomes to CPP based upon which compliance option is adopted and how states and power systems group together to achieve these targets. In this insight, we go through the CPP rulemaking process, compliance mechanisms, and compliance outlook relative to our H1 reference cases.