"A clean energy standard (CES) has been identified as one possible legislative option to encourage a more diverse domestic electricity portfolio. A CES could require certain electricity providers to obtain a portion of their electricity from qualifying clean energy sources. A CES is broader than a renewable energy standard (RES), including 'clean' energy sources along with renewable energy sources. The RES has been a topic of legislative attention since at least the 105th Congress. Some assert that a CES could lead to economic growth, reduce greenhouse gas emissions, and secure U.S. leadership in clean energy technology. Others argue that a CES could lead to higher electricity prices, necessitate additional financial investment in grid infrastructure, and - in some cases - depend on energy technologies that are not yet established for widespread commercial scale use. [...] Many questions will need to be answered if a CES is established. How much clean electricity can be generated from each qualifying energy source, given the proposed CES time frame? Should a carbon accounting parameter be assigned to each source? Will a time come when some resources (e.g., wind, solar) used to generate clean electricity cease to be considered a 'free' resource? Should energy efficiency be included in a CES, and if so, how should it be included? How would a CES interact with state renewable electricity requirements? Who would assume the costs of new transmission capacity?"
CRS Report for Congress, R41797