Oregon passed a net metering law in 1999 that helped encourage installation of small wind power systems.[3] Under Senate Bill 838, wind, solar, geothermal and other types of renewable power must account for 25 percent of an electric utility's retail sales by 2025.[5] The US Energy Information Administration expects this to increase windpower in Oregon, as older hydropower is exported to California and not eligible for the RPS.Estimates from the National Renewable Energy Laboratory showed that Oregon has potential to install over 27,000 megawatts of onshore wind power.[23][24] About four gigawatts of new wind energy development in Eastern Oregon and Washington has not been built due to the interference it could cause with aviation radar.