The California Public Utilities Commission is considering allowing renewable energy credits to count toward utilities' 20 percent renewables portfolio standard to increase compliance flexibility. A white paper released by the CPUC April 20 analyzes the pros and cons of various green credit programs in the U.S. It concludes that creating a California program could help reach the state's renewables goals at "least cost." Renewable credits, or green tags, represent the renewable green attribute of a power source separate from the actual energy supplied. There have been unsuccessful legislative attempts to create a green tag trading system in the state. Supporters have contended, however, that the CPUC has the authority to create such a program. The commission's paper Renewable Energy Certificates and the California RPS Program explains that the location of renewables projects, the distance away from areas of demand, and transmission constraints create RPS compliance difficulties for some utilities and power suppliers, particularly small ones. For example, the Tehachapi Mountains represent an area of low-cost wind potential for Southern California that exceeds Southern California Edison's renewables portfolio standard mandate. Entities outside Edison's territory may find it uneconomic to contract with these wind developers because of the costs of managing delivery or remarketing of the energy, the study notes. "As a result, much of this resource potential could go untapped." The paper also warns that a renewable energy credit program could dilute the benefits sought by the state renewables portfolio standard. If credits replace added new renewable supplies, that would be one of the program's drawbacks.