Many states have established standards for renewable energy production and sales in the form of a Renewable Portfolio Standard (RPS). An RPS specifies that a minimum percentage of the total energy a utility company sells must come from renewable sources such as solar power, wind power, or biomass.  While there is no federal RPS, eighteen states and several municipalities throughout the country (as well as many countries) have enacted voluntary or mandatory standards. This report discusses the benefits and drawbacks associated with RPS and reviews the existing RPS, including eligible sources, for these eighteen states and several U.S. municipalities.