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USA: Most pumped storage electricity generators in the U.S. were built in the 1970s


Source: US Energy Information Administration

October 31, 2019

Pumped storage plants for hydroelectric power in the Unites States were built primarily between 1960 and 1990; nearly half of the pumped storage capacity still in operation was built in the 1970s. Pumped storage power plants are the largest source of electricity storage technology used in the United States, both in terms of capacity and number of plants. (Virtually all remaining commercial-sized electrical storage use thermal energy or batteries.)

Pumped storage involves pumping water into a storage reservoir during times of relatively low electricity demand and low electricity prices, such as during the night. When electricity demand is high, water flows downhill from the reservoir through hydroelectric generators at a dam. Pumped storage plants cost more to construct than conventional hydro plants because of the storage reservoirs, additional pipes, and pumps that carry water from the reservoir to the dam. They also incur a sizable additional operating expense from pumping water uphill.

In 2018, the United States had 22.9 gigawatts (GW) of pumped storage hydroelectric generating capacity, compared with 79.9 GW of conventional hydroelectric capacity, according to the U.S. Energy Information Administration’s (EIA) most recent inventory of power plants. California has the most pumped storage capacity, with 3.9 GW, or 17% of the national total. Other states such as Virginia, South Carolina, and Michigan each have at least 2 GW of hydroelectric pumped storage capacity.

Pumped storage hydropower systems are generally one of two types. An open-loop system has a continuous source of downstream water that is pumped uphill to an upper storage reservoir. Typically, an open-loop plant pumps water that has already passed through the dam up to the storage reservoir above the dam. By contrast, closed-loop systems pump water from a lower storage reservoir, which is not continuously filled with water and is generally not connected to a flowing source.

Historically, most U.S. pumped storage plants were installed on rivers as open-loop systems. However, more of the recent applications filed with the Federal Energy Regulatory Commission (FERC) for pumped storage hydro project licenses have been for closed-loop plants. One reason for the increase in closed-loop plants is that they capture streams of runoff water from agricultural irrigation systems that would otherwise go unused.

Even though FERC has issued licenses for three proposed pumped storage projects since 2014, no new pumped storage projects have come online in the United States since 2012. EIA’s most recent survey of planned power plant additions shows no pumped storage projects under development.

Because these plants require energy to pump water uphill, pumped storage hydro plants have net negative electricity generation balances, meaning that they consume more energy than they store. Most pumped storage systems require 15% to 30% more electricity to pump water uphill than what the water generates when it flows back downhill.

To provide a better understanding of how electricity storage systems are used, EIA recently added tables to its Electric Power Annual that show adjusted capacities and usage factors for the two main energy storage technologies: pumped storage and batteries. Each month, pumped storage systems operate at between 8% and 17% of their capacity. Pumped storage’s usage factor generally follows the pattern of total electricity demand: a large peak in the summer months, a smaller peak in the winter months, and the lowest use in the spring and fall.

Principal contributor: Fred Mayes



Eric Smith's picture
Eric Smith on Nov 1, 2019 3:08 pm GMT

Closed loop pumped storage does have some geographic limits, but are not nearly as restricted as sites for conventional hydropower. Unfortunately, they are subject to the same political restrictions. Perhaps the most ambitious proposal is to convert the Hoover dam into a large open loop pumped stroage unit bu building a new lower resrvoir downstreamm of the existing dam. If they can get the land use permits, this would bet my vote. Unfortunately, as a resident of south Louisiana, our topography argues against the use of either hydro power or pumped storage.

One related option under consideration, primarily in England, is the use of liquefied air as a storage medium.

Michael Spindler's picture
Michael Spindler on Nov 8, 2019 10:58 pm GMT

There has been a privately funded closed loop system recently fast tracked in southern part of Washington State. The Goldendale Pumped Storage Project (GPSP), is 2 billion dollar private investment and is certainly cost effective and efficent on paper.  It will use surplus solar energy from California to run the pumps. I also note that it is possible to run the pumps in a closed loop system with solar energy stored in batteries on site too for future projects.

The question about using more electricity for the pumps than it produces is really moot today when considering the above. And pumped storage is used mainly for peak loads as well, not as baseload power, although it could be used for that for short periods of time too.


Eric Smith's picture
Eric Smith on Nov 11, 2019 6:22 pm GMT


The plant in Washington State sounds like a great approach, although I would think they would start by using their own surplus wind power to pump water uphill. That is certainly a closer, and probably more concentrated source, than transmitting California solar power to Washington, then reversing the flow during the early evening peak demand period in California. Since distance increases the transmission cost, the closer the source the better. As for using chemical batteries, that sounds like a nonstarter, given the disparity in capital cost between pumped storage and  batteries with the same storage and discharge capacity.


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