These states have set standards specifying that electric utilities generate a certain amount of electricity from renewable sources. Most of these requirements take the form of “renewable portfolio standards,” or RPS’s, which require a certain percentage of a utility’s power plant capacity or generation to come from renewable sources by a given date. The standards range from modest to ambitious, and definitions of renewable energy vary. Though climate change may not be the prime motivation behind some of these standards, the use of renewable energy does deliver significant GHG reductions. For instance, Texas is expected to avoid 3.3 million tons of CO2 emissions annually with its RPS, which requires 2,000 megawatts of new renewable generation by 2009. Increasing a state’s use of renewable energy brings other benefits as well, including job creation, energy security, and cleaner air.

Some of these efforts have been particularly successful. For example, Connecticut increased its RPS in 2003, extending the standard to all utilities in the state. Iowa met its standard in 1999. Many states allow utilities to comply with the RPS through tradeable renewable energy credits. While the success of state efforts to increase renewable energy production will depend in part on federal policies such as production tax credits, states have shown considerable efficacy in encouraging clean energy generation.