Salt River Pumped Storage Project

About the project

SRP has been operating pumped storage units on the Horse Mesa and Mormon Flat dams for over 50 years.

As part of the Salt River Pumped Storage Project, SRP is exploring opportunities to expand pumped storage hydropower on the Salt River reservoir system.

SRP is evaluating the potential for a new pumped storage hydropower facility to pair with Apache Lake on the Salt River. The pumped storage hydropower facility would require construction of a new reservoir to act as the upper reservoir and additional transmission infrastructure to connect to SRP’s existing 500-kilovolt (kV) Coronado-Silver King transmission line. The proposed pumped storage sites and transmission infrastructure routing options are depicted in the study area map.

The results from the engineering design efforts, environmental surveying and public input are assisting SRP in evaluating the pumped storage site and transmission routes for permitting efforts.

SRP is making transformative changes to its power generation resource portfolio in the face of unprecedented project load growth within its electric service territory. SRP needs to increase reliable, resilient and readily dispatchable energy to serve this growing demand. SRP is exploring a pumped storage hydropower option that would add up to 2,000 megawatts (MW) of energy storage capacity near Apache Lake on the Salt River.

Stay informed

The Notice of Intent to complete an Environmental Impact Statement (EIS) for the Salt River Pumped Storage Project was published in the Federal Register on June 30, 2026. This is the official start of the National Environmental Policy Act (NEPA) process, which will result in the development of the EIS.

The NEPA process begins with a 30-day public comment period. During this 30-day period, three different public meetings will be held — two virtual meetings and one in-person open house meeting. The NEPA process will be led by the Bureau of Reclamation. Further information on the NEPA process and the dates and locations of the public meetings can be found on  this webpage (Opens in a new tab) .

The EIS will take approximately two years to prepare; the final EIS is expected in summer 2028. Get Involved – Salt River PSP (Opens in a new tab)

How pumped storage hydropower works

Pumped storage hydropower facilities store and generate electricity by moving water between two reservoirs at different elevations.

Morning and midday

When electricity demand is lower and SRP has excess supply available, the turbines spin backward to pump the water back into the upper reservoir so it can be used again to generate power. As SRP adds more energy to the grid in the coming years, we expect that the amount available will exceed demand during the morning and midday periods.

Late afternoon and overnight

To generate electricity when power from the plant is needed, water is released from the upper reservoir through hydropower turbines that rotate generators to produce electricity. The water flows into the lower reservoir where it stays until electricity demand lowers.

Pumped storage project videos

Benefits of pumped storage hydropower

Pumped storage hydropower provides a large-scale way to store and deliver electricity to customers. Below are some of the reasons we’re planning to add it to our power generation sources.

Supports grid reliability

Generating pumped storage hydropower helps SRP diversify our resource portfolio. That means the energy we produce is more reliable, more diverse, and less sensitive to supply chain or market shocks that could negatively impact prices.

Boosts energy storage supply

Pumped storage hydropower can also play a key role in helping us store excess energy that’s generated during the day so it can be used at night when demand is highest. One facility can provide 10 hours of energy storage.

Supports the grid of the future

Another benefit of pumped storage hydropower is that it supports meeting SRP’s Integrated System Plan, a holistic roadmap for the power system of the future. It considers evolving customer needs for reliability, affordability and sustainability.

Past success and future potential

SRP has a long history of successfully operating hydropower generating facilities on the Salt River.

Currently, SRP generates 265 MW of hydropower at the four dams located on the Salt River. That’s enough to power more than 60,000 average-sized homes. Two of those dams, Horse Mesa and Mormon Flat, have generators capable of pump-back operation with a total capacity of over 150 MW.

The new pumped storage facility would have a capacity of between 1,000 MW and 2,000 MW — enough power to serve approximately 225,000 to 450,000 homes for 10 hours after each time the reservoir refills.

Project timeline: Target in service by 2033

Following engineering feasibility assessments and environmental permitting, SRP could decide to begin construction in 2027.

This timeline would allow SRP to construct the facility for an online date of 2033 to help meet SRP's significant resource needs in early 2030.

Past events

Events in 2025

SRP hosted the following public meetings in May 2025.

Events in 2024

SRP hosted the following public meetings in April 2024.

Events in 2023

SRP hosted the following public meetings in November 2023.

Public input process

As this project moves forward, there will be a variety of opportunities for public input. SRP will provide more information here as opportunities for public input become available.

FAQ

Contact us

If you have questions about the project, please call (602) 236-2872 or email [email protected].