The report indicates that hydropower plays an important role in the U.S. power system, accounting for approximately 7% of installed capacity and about 7.1% of generation (both excluding pumped storage plants). Over the past 100 years, the United States has built 2,198 hydropower plants with a total installed capacity of 79.64 gigawatts, with half located in Washington, California, and Oregon. Although development has been slow in recent years, with only 1.48 gigawatts of new capacity added from 2005 to 2013, hydropower remains the largest source of renewable energy electricity in the United States, with an average generation of 288 terawatt-hours from 2011 to 2013. The capacity factor of hydropower plants has shown a declining trend in recent years, at 46% in 2011, 40% in 2012, and 39% in 2013; and since most hydropower plants were built before 1970, the capacity factor is expected to continue to decline in the long term.
As of the end of 2014, there were 331 hydropower projects in development in the United States, with a total installed capacity of 4.37 gigawatts, of which 407 megawatts were under construction, and 263 megawatts had received permits, while the majority were still in the early stages of feasibility studies and permit applications. Since 2005, new hydropower capacity brought online in the United States has primarily been upgrades to existing projects, with the industry investing at least $6 billion in refurbishing, replacing, and upgrading hydropower plants.
The United States currently has 42 pumped storage plants with a total installed capacity of 21.6 gigawatts, three-quarters of which are large-scale (greater than 500 megawatts), demonstrating significant economies of scale. Most of these plants were built between 1960 and 1990. Pumped storage in the United States accounts for the vast majority (97%) of utility-scale electricity storage capacity. As of the end of 2014, there were still 51 projects totaling 39 gigawatts in development, with installed capacities of 150 megawatts and above, averaging 787 megawatts. Unlike existing pumped storage projects that serve as a supplement to nuclear or fossil fuel baseload, newly developed pumped storage plants aim to provide a range of ancillary services to support the integration of variable renewable energy sources.
Hydropower projects not only supply electricity, but at least 84% of plants also provide additional functions, including recreational activities, flood control, irrigation, navigation, and water supply. Federal agencies own nearly half (49%) of the hydropower installed capacity, but most are large hydropower plants, accounting for only 8% (176 plants) in number; public utilities, state governments, and power cooperatives own 24% of the hydropower installed capacity; the private sector owns 27% of the hydropower installed capacity, mostly small and medium-sized plants, accounting for 62% of the total. The U.S. hydropower industry has created over 55,000 direct jobs, with hydropower supply chain companies present in all 38 states, and at least 172 manufacturing companies producing one or more major hydropower components, including turbines, generators, transformers, penstocks, spillways, and valves. Since 1996, Voith has been the largest turbine manufacturer in the United States, with Alstom ranking second.