In Maricopa County, Arizona (AZ). The map on this page is placed at the coordinates EIA files for the plant, which locate the site rather than any individual unit.

How big is Horse Mesa?

131 MW of nameplate capacity across 4 units, as of the EIA-860M release for 2026-07.

EIA-860M names Salt River Project as the reporting entity. That is the operator of record on the survey, which is not always the ultimate owner.

Is this the same as Horse Mesa LLC?

Probably, but EIA-860M does not say. The survey records a plant name and a reporting entity — Salt River Project here — not the project company that holds the asset. Project companies are commonly registered as an LLC carrying the plant's name, so a search for "Horse Mesa LLC" usually means this site. This page shows only what EIA files, and does not assert a corporate structure it cannot see.

Is Horse Mesa still running?

EIA-860M files it as "Operating" for 2026-07. Statuses change monthly, and this page follows the monthly release.

Horse Mesa

Horse Mesa is a 131 MW pumped storage hydro plant in Maricopa County, Arizona, operated by Salt River Project. EIA-860M lists 4 generating units here. Its units entered service in 1927.

As of 2026-07 (inventory dated 2026-07-31) · EIA-860M Preliminary Monthly Electric Generator Inventory · eia.gov/…/july_generator2026.xlsx · eia.gov/…/eia860m

Nameplate capacity: 131.3 MW; 149 MW net summer
Generating units: 4
In service: 1927
EIA plant ID: 145

Where it is

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County: Maricopa County, Arizona
Coordinates: 33.5907, -111.344
Balancing authority: SRP
Sector: Electric Utility

Units, technology and status

Operator of record: Salt River Project
Primary energy source: Pumped storage
Technologies: Conventional Hydroelectric, Hydroelectric Pumped Storage
Status: Operating (3) · Out of service but expected to return to service in next calendar year (1)

This site runs on more than one energy source. EIA-860M capacity splits: Pumped storage 100 MW, Hydro 32 MW. It is filed here under Pumped storage, the source with the most capacity.

Every plant Salt River Project reports to EIA →

Horse Mesa: FAQ

Where is Horse Mesa?: In Maricopa County, Arizona (AZ). The map on this page is placed at the coordinates EIA files for the plant, which locate the site rather than any individual unit.
How big is Horse Mesa?: 131 MW of nameplate capacity across 4 units, as of the EIA-860M release for 2026-07.
Who owns Horse Mesa?: EIA-860M names Salt River Project as the reporting entity. That is the operator of record on the survey, which is not always the ultimate owner.
Is this the same as Horse Mesa LLC?: Probably, but EIA-860M does not say. The survey records a plant name and a reporting entity — Salt River Project here — not the project company that holds the asset. Project companies are commonly registered as an LLC carrying the plant's name, so a search for "Horse Mesa LLC" usually means this site. This page shows only what EIA files, and does not assert a corporate structure it cannot see.
Is Horse Mesa still running?: EIA-860M files it as "Operating" for 2026-07. Statuses change monthly, and this page follows the monthly release.