Over 90% of the United States’ energy storage capacity comes from pumped storage hydropower. All new US storage additions are electrochemical based (e.g., lithium-ion batteries), with utility-scale systems representing most of this rapidly growing sector.

Energy storage is becoming more important than ever to balance a growing power generation fleet made of intermittent renewables.

But no new large pumped storage hydropower (PSH) has completed constructed in the United States since the 1990s, despite that it is by far the largest source of existing energy storage.

A May 2022 study from the National Renewable Energy Laboratories sought to clarify the US’ technical potential for new PSH using a GIS-based analysis, and found “technical potential for 35 terawatt-hours (TWh) of energy storage across 14,846 sites, which represents 3.5 terawatts (TW) of capacity when assuming a 10-hour storage duration.”

Where are the areas with the densest potential and with the lowest-cost sites?

If you looked at a U.S. topographic map, it’d be where there are big elevation differences.

That’s because a flow of water sluicing through a turbine can create power more efficiently the steeper it drops.

The NREL model looked solely at “closed-loop systems that have no ongoing hydrologic relationship with existing natural water bodies, which can reduce environmental impacts relative to open-loop systems.” They also sought existing dry-gully features which can minimize the costs of creating them artificially.

This graphic map has already filtered out areas with potential development barriers:
–  Legislatively protected and critical habitat areas
–  Incompatible land use areas (city, swamp, ice)
–  Intersections with existing water features

That left under one million upper and lower reservoirs out of the 11 million modeled. Once upper and lower reservoirs were paired and a least-cost optimization was applied, 14,846 systems remained, representing the technical potential for closed-loop pumped storage hydropower in the United States.

The technical potential analysis can be found here: