Power project
Sierra Estrella Energy Storage
Avondale, Arizona · Storage
In service — documented
SRP identifies Sierra Estrella as a 250 MW, four-hour battery that entered service in 2024.
Four hours is the rated duration. The 1,000 MWh value below is calculated from 250 MW × four hours, not a separate measured dispatch result.
Last documented milestone:
Sources checked: September 7, 2026
- Developer / operator
- Plus Power; Salt River Project
- Technology
- Grid-charged battery storage
What the equipment is rated to do
Capacity is not annual energy output or guaranteed availability. MW and MWh describe different quantities.
The documented hurdles
No specific blocking cause established in the linked record.
The dated trail
New battery celebrated by utility
SRP’s June announcement describes Sierra Estrella separately from the smaller Superstition battery. Its project register lists 2024 commercial operation.
Open the supporting records
1. Utility project register · Salt River Project
SRP solar and storage project register
A nameplate rating and service year are not measured daily dispatch or proof of continuous availability.
Publication: Current page; checked September 7, 2026 · Checked: 2026-09-07
Source record: srp-battery-register
Location in source: Table: Sierra Estrella Energy Storage, 250 MW four-hour battery, 2024 commercial operation2. Utility announcement · Salt River Project / Plus Power
Sierra Estrella battery joins SRP’s system
The announcement covers two batteries. Only Sierra Estrella’s 250 MW is assigned to this record, not the combined 340 MW.
Publication: 2024-06 · Checked: 2026-09-07
Source record: sierra-estrella-operation
Location in source: Sierra Estrella section: 250 MW facility; four-hour operating description