Survey of Energy Resources 2007
Hydropower Country Notes
United States of America
The hydro resource base is huge: the gross theoretical potential was assessed in 1979 as 512 GW, equivalent to 4 485 TWh/yr. The United States WEC Member Committee has reported that the annual technically exploitable capability is 1 752 TWh, of which 501 TWh is economically exploitable, both based on publications of the Idaho National Environmental and Engineering Laboratory. The end-2005 US hydro capacity of 77.4 GW had an average annual capability of about 292 TWh, equivalent to 58% of the assessed economic potential.
Actual hydroelectric output of 269.6 TWh in 2005 accounted for 6.7% of US electricity generation. Only 8 MW of hydro capacity was under construction at end-2005, and 16 MW was at the planning stage.
The reported technically exploitable capability of small-scale hydropower is almost 584 TWh. The installed generating capacity of small hydro plants totalled 2.84 GW at end-2005; actual generation in 2005 was about 10.7 TWh, equivalent to 4% of total US hydro output.