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.

Updated proposed project features

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.

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.

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.