A standard for planning and acquiring fuels for producing electricity which is based on the renewability of those fuels. When this standard is applied to energy producers in the US, the producer's total source energy, also referred to as its portfolio, must consist of a certain percentage of renewable fuels, preferably nonpolluting source energy such as wind and solar. The percentage is usually small and in some circumstances it may be negotiable. As of early 2001, the RPS requirement for many states was 3% total renewable energy in a producer's portfolio by 2005.

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