On June 25, 2013, President Obama called on the U.S. Environmental Protection Agency (EPA) to propose a rule to regulate greenhouse gases from existing power plants by June 2014. Section 111(d) of the Clean Air Act is likely to be the authority upon which EPA relies to draft the rule. With the drafting of these regulations, a whole host of questions emerge concerning what a greenhouse gas regulatory scheme might look like. One of the most promising opportunities for emission reductions from existing sources is in low-cost end-use energy efficiency. This report makes several recommendations for how a 111(d) rulemaking could be designed so that end-use efficiency plays a role in achieving meaningful greenhouse gas reductions from the power sector.