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| Fig. 1: Hydroelectric Generation and Its Share of Total U.S. Electricity, 2013-2023. [2] (Image Source: J. Liu) |
Hydroelectric power has been a cornerstone of renewable energy in the United States, offering a clean and reliable source of electricity for over a century. While it accounted for as much as 40% of U.S. electricity production in the 1920s, its share has declined due to the rapid growth of other energy sources, such as fossil fuels and, more recently, wind and solar power. [1] Despite this, hydroelectric power remains a critical component of the U.S. energy mix, contributing about 5.8% of total electricity generation in 2023. [2]
From 2013 to 2023, U.S. hydroelectric generation fluctuated between 245 and 300 terawatt-hours (TWh) annually as shown in Fig. 1. [2] This variability is largely influenced by hydrological conditions, such as rainfall and snowmelt, which directly affect water availability. For instance, drought conditions in the western United States in recent years have constrained hydroelectric output, while wetter years have supported higher generation levels. [3]
The U.S. hydropower fleet includes 2,252 plants with a total generating capacity of 80.92 GW and an estimated energy storage capacity of 553 GWh, which produced approximately 266 TWh of electricity in 2022. [4] This represents about 6.2% of all electricity generated that year. [4] The Hoover Dam, one of the most iconic hydroelectric projects in the U.S., built in the 1930s, exemplifies the large scale hydroelectric infrastructure constructed during the early 20th century (see Fig. 2).
The efficiency of existing hydroelectric infrastructure has remained high, with most plants achieving operational efficiencies exceeding 90%. Despite this, no major capacity expansions have occurred, as large-scale dam construction has slowed since the mid-20th century due to environmental and regulatory challenges. [1,5]
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| Fig. 2: Picture of Hoover Dam (Built in 1930s). (Image Source: J. Liu) |
While hydroelectric power has historically dominated U.S. renewable energy, its share has declined in recent decades as wind and solar capacity expanded rapidly. In 2023, hydro accounted for about 27% (245 TWh) of total renewable electricity generation, compared to about 47% from wind (421 TWh) and 27% from solar (239 TWh). [2] However, unlike wind and solar, hydroelectricity provides consistent and dispatchable power, making it a critical resource for grid stability.
The role of hydroelectric power in the U.S. is expected to remain stable in the coming decades, with modest capacity upgrades rather than new large-scale projects. The net increase in U.S. hydropower capacity from 2010 to 2022 was 2.1 GW, comprising upgrades to existing plants (1.6 GW), new projects (0.7 GW), and retirements (-0.2 GW). [4] These capacity additions demonstrate a focus on modernizing and extending the lifespan of existing facilities rather than constructing new dams. Emerging technologies like hybrid hydropower-battery systems and pumped-storage hydropower (PSH) offer opportunities for future innovation. These systems can support intermittent renewable sources such as wind and solar, providing crucial energy storage and grid balancing services. [4]
Hydroelectric power remains a vital, though declining, component of the U.S. energy mix. While it faces challenges from climatic variability, aging infrastructure, and environmental considerations, its ability to provide reliable and flexible energy will ensure its continued importance in the transition to a cleaner energy future.
© Jerry Liu. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] "Hydroelectric Power," U.S. Bureau of Reclamation, July 2005.
[2] "Electric Power Annual 2023," U.S. Energy Information Administration, October 2024.
[3] S. W. D. Turner et al., "Drought Impacts on Hydroelectric Power Generation in the Western United States," Pacific Northwest National Laboratory, PNNL-33212, September 2022.
[4] "U.S. Hydropower Market Report, 2023 Ed.," U.S. Office of Energy Efficiency and Renewable Energy, DOE/EE-2771, October 2023.
[5] A. Osmani et al., "Electricity Generation From Renewables in the United States: Resource Potential, Current Usage, Technical Status, Challenges, Strategies, olicies, and Future Directions," Renew. Sustain. Energy Rev. 24, 454 (2013).