DOE Study Maps 15.2 TWh of Untapped Hydropower at US Non-Powered Dams

What the Updated Non-Powered Dam Assessment Shows

Researchers at the Department of Energy’s Oak Ridge National Laboratory and Idaho National Laboratory have published a more detailed estimate of electricity that could be produced by adding turbines to existing non-powered dams across the United States. The updated assessment puts the technical potential at as much as 15.2 terawatt-hours per year.

Only about 3% of U.S. dams currently generate hydropower. The rest are used for water storage, navigation and flood control, and the two national laboratories view those non-powered structures as a largely untapped domestic energy asset. A previous Oak Ridge assessment had identified about 4 gigawatts of potential capacity across more than 2,600 non-powered dams, with an average facility size of roughly 1.5 megawatts.

The new work is meant to address weaknesses in earlier estimates, which ranged widely between 12 and 30 GW because of limited data. Using Idaho National Laboratory’s HydroGenerate tool and daily streamflow records, the researchers modeled design flow, hydraulic head, turbine efficiency, plant capacity and seasonal water availability to produce a more site-specific picture. The tool is available as an open-source package so project developers can validate their own assessments.

Why Federally Owned Dams and the Upper Mississippi Could Anchor Development

A federally concentrated opportunity

Federally owned dams account for 86% of the identified potential capacity. That makes agencies such as the Army Corps of Engineers central to whether this resource is developed. The practical consequence is that financing, authorizations and project selection for most of the opportunity would be driven by federal priorities rather than by independent developers moving alone.

The upper Mississippi and Great Lakes stand out

Oak Ridge identified the upper Mississippi River and Great Lakes as particularly promising because they contain many high-capacity candidate sites. Many of the dams in that corridor already serve navigation and flood control, which means retrofitting could add electricity without creating new reservoirs. At the same time, those existing functions limit how aggressively a site can generate power, so the new streamflow-based modelling is important for realistic sizing.

Technical potential is not a project pipeline

The 15.2 terawatt-hour figure is a best estimate of what is technically possible, not an economic or regulatory plan. Hydropower retrofits still face environmental reviews, grid interconnection studies, licensing and long construction timelines. The researchers acknowledge that development can take decades, which is why the next phase of the work will incorporate future streamflow variability and extend the assessment to Alaska and Hawaii.

Next Steps for Utilities, Developers and Agencies

• Federal dam owners and their partners should use the refined Oak Ridge data to rank candidate sites on the upper Mississippi River and Great Lakes, where federally owned dams account for most of the identified potential.
• Utilities, developers and state or local agencies can apply the open-source HydroGenerate tool to screen smaller non-federal dams, which average about 1.5 MW and may fit local or utility-scale projects.
• Project developers should treat the 15.2 TWh estimate as a technical ceiling, then add economic, environmental, licensing and interconnection feasibility layers before selecting sites.
• Policymakers and regulators should align hydropower decisions with the forthcoming streamflow-variability data and the planned Alaska and Hawaii expansion, since long development times require planning for future water availability.