At the end of September 2008, the United States wind power installed nameplate capacity was 21.02 GW, which is enough to serve 5.6 million average households. $9 billion was invested in 5.3 gigawatts of new U.S. wind power capacity in 2007, causing the total U.S. wind power capacity to increase by 46%. Wind power accounted for 35% of all new U.S. electric generating capacity in 2007. American wind farms will generate an estimated 48 terawatt-hours (TWh) of wind energy in 2008, just over 1.5% of U.S. electricity supply. In addition, new transmission facilities under development throughout the country should allow the future development of at least another 200 gigawatts of wind power.