The Public Utility Regulatory Policies Act was a law passed in 1978 by the U.S. Congress as part of the National Energy Act. It was meant to promote greater use of renewable energy. This law created a market for non-utility electric power producers forcing utilites to buy power from these producers at rates that are generally good for the producers. One effect of the law is that now 7% of the power produced in the U.S. comes from non-utility sources. The biggest result has been the prevalence of cogeneration plants, which produce electric power and steam. PURPA is starting to become out of date, since many of the contracts made under it during the 1980s are expiring. However, it is still the most important piece of legislation for promoting renewable energy.