still provide a very small proportion of the U.S. total (about 2.5 percent of all electricity generated). In the 2008 reference-case estimates of the Energy Information Administration (EIA, 2008), the contribution of nonhydroelectric renewables was projected to be about 7 percent of total electricity generation by 2030. But the AEF Committee found that with a sustained effort and accelerated deployment, nonhydroelectric renewables could collectively provide 10 percent of the nation’s electricity generation by 2020 and 20 percent or more by 2035. With current hydropower included, more than 25 percent of electricity generation could come from renewables by 2035.
Renewables currently represent a small fraction of total electricity generation. According to the EIA, conventional hydroelectric power is the largest source of renewable electricity in the United States, generating about 6 percent (almost 250,000 GWh out of a total 4 million GWh) of electricity produced by the electric power sector in 2007.10
The largest growth rates in renewable resources for electricity generation are currently in wind power and solar power. Though wind power in 2007 represented less than 1 percent of total electricity generation, wind electricity grew at a 15.5 percent compounded annual growth rate over the 1990–2007 time period and at a 25.6 percent rate between 1997 and 2007.
In 2007, wind power supplied over 34,000 GWh, almost 8,000 GWh more than in the year before. An additional 8,400 MW of capacity was added in 2008, representing an additional yearly generation of 25,000 GWh (assuming a 35 percent capacity factor). Total wind power capacity at the end of 2008 was approximately 25,000 MW. However, the overall economic downturn at that time caused financing for new wind power projects and orders for turbine components to slow, and layoffs in the wind turbine-manufacturing sector began. Thus, 2009 recently looked to be considerably smaller in terms of new capacity than 2008. However, recent data reveal that 2.8 GW of new wind power generation capacity was installed in the first quarter of 2009. Over the long term, the impacts of state renewable portfolio standards and the federal production tax credit will continue to spur installation of wind power capacity.