In 2016, nearly 300 megawatts (MW) of electricity generating capacity is expected to come online from dams that did not previously have electric generating units, commonly referred to as nonpowered dams (NPDs). NPD capacity additions make up 92% of the 320 MW of planned hydroelectric capacity for 2016. Expected capacity additions at NPDs in 2016 are large compared to recent NPD additions, which totaled 126 megawatts (MW) over 2006–15, but relatively small compared with total U.S. hydroelectric capacity of nearly 80,000 MW as of April.
The National Hydropower Association estimates that 3% of the nation’s 80,000 dams currently generate electricity. Existing conventional hydroelectric generators in the United States provided 251 million megawatthours of electricity in 2015, or about 6% of annual total net generation. Unlike other forms of renewable-fueled electricity, such as solar and wind, hydroelectric capacity additions have been relatively modest in recent years. Also, about 1,000 MW of hydroelectric capacity has been decommissioned over the 2006–15 period, mainly through the removal of existing dams. New conventional hydroelectric generators may not be eligible for federal tax credits, unlike new wind and solar additions. Depending on the state, hydroelectric generation may not be eligible for compliance with state renewable portfolio standards or voluntary goals.
Although electric generating units have been installed at NPDs throughout the country, the Ohio River accounts for much of this activity. About 74% of all the new and planned NPD capacity additions from 2006 to 2016 occurred along the Ohio River. Many of the existing dams along the Ohio River that have been or will be converted to produce electricity are used to maintain navigable depths during periods of low water flow.
In a study of hydroelectric potential at NPD, the U.S. Department of Energy (DOE) estimated that as of 2012, NPDs had the potential to add 12,000 MW of additional generating capacity, with about 3,000 MW of capacity in the Ohio River region alone. Since then, four NPD projects have begun construction: Cannelton, Meldahl, and Smithland in Kentucky, and Willow Island in West Virginia. Once these projects are completed, the total hydroelectric capacity along the Ohio River will increase by 313 MW to a total of 554 MW. As a result of these NPD capacity additions, Kentucky and West Virginia will increase their hydroelectric capacities by roughly 32% and 15%, respectively, in 2016.
The DOE study only assessed technological potential based on the energy density of the water flow at certain stream segments across the United States. The study did not address the economic, regulatory, and political hurdles that may affect actual development of hydroelectric projects.