Most proposals for a Clean Energy Standard (CES) include energy efficiency. Efficiency was included in CES proposals introduced by Senators Lugar (S. 3464) and Graham (S. 20) in the 111thCongress. CES proposals by Third Way and the Center for American Progress also include efficiency. Senator Murkowski proposed an amendment to permit unlimited efficiency in the Renewable Energy Standard (RES) reported out by the Energy and Natural Resources Committee in the last Congress. Only President Obama has not included energy efficiency in his CES proposal, although reportedly this decision is being reconsidered. This short fact sheet addresses a few questions about efficiency in a CES.