Pumped storage projects move water between two reservoirs located at different elevations (i.e., an upper and lower reservoir) to store energy and generate electricity. Generally, when electricity demand is low (e.g., at night), excess electric generation capacity is used to pump water from the lower reservoir to the upper reservoir. When electricity demand is high, the stored water is released from the upper reservoir to the lower reservoir through a turbine to generate electricity. Pumped storage projects are also capable of providing a range of ancillary services to support the integration of renewable resources and the reliable and efficient functioning of the electric grid. View Diagram of a Pumped Storage Project.

The Commission has authorized a total of 24 pumped storage projects that are constructed and in operation, with a total installed capacity of approximately 16,500 megawatts. Most of these projects were authorized more than 30 years ago.

Recent Developments at FERC
In the last few years, the Commission has seen an increase in the number of preliminary permit applications filed for pumped storage projects. A preliminary permit does not authorize construction, but it maintains priority of application for license (i.e., guaranteed first-to-file status) while the permittee studies the site and prepares to apply for a license.

Many of the recently-proposed pumped storage projects can be classified as using a closed-loop system. We define:

• Closed-loop pumped storage as projects that are not continuously connected to a naturally-flowing water feature; and
• Open-loop pumped storage as projects that are continuously connected to a naturally-flowing water feature.

Differentiating between open- and closed-loop systems is helpful for illustrating trends in pumped storage project proposals, but project-specific impacts (rather than the open- vs. closed-loop classification) are the primary concern during the licensing process.

To view a bar chart illustrating trends in preliminary permit application filings, see:

• » Preliminary Permit Application Trends for Open- and Closed-Loop Pumped Storage Projects Bar Chart (2001-2011) updated 01/01/2012

Existing and Proposed Projects
To view maps illustrating the location, capacity, and project type (open- vs. closed-loop) of existing and proposed pumped storage projects, see:

• » Licensed Pumped Storage Projects Map updated 07/01/2012
• » Pending Licenses and Relicenses for Pumped Storage Projects Map updated 07/01/2012
• » Issued Preliminary Permits for Pumped Storage Projects Map updated 07/01/2012
• » Pending Preliminary Permits for Pumped Storage Projects Map updated 07/01/2012

For information on specific projects, including issued licenses and exemptions; pending licenses, relicenses, and exemptions; issued preliminary permits; and pending preliminary permits, see our main Licensing page.