It is the tenth battery energy storage system (BESS) project Invenergy has put into commercial operations in the state, all of which are in Maricopa and Yuma Counties and have agreements with utility Arizona Public Service (APS).
Brian Cole, VP resource management at APS, commented: “Arizona has experienced an extended stretch of triple-digit temperatures this summer and APS customers have used a record-breaking amount of energy as they run their air conditioners to stay cool.”
“Adding renewable projects like the El Sol Energy Storage Center to our already diverse power supply will help APS continue to deliver the reliable, affordable and increasingly clean energy our customers count on, especially on our hottest summer days.”
The table below shows all of Invenergy’s BESS projects in Arizona, including commercial operation date (COD). Ten are in operation with an 11th, Yuma Storage, set to come online this year too.
| Name | County | MW | MWh | COD |
| Cotton Center | Maricopa County | 17 | 51 | 2023 |
| Desert Star | Maricopa County | 10 | 30 | 2023 |
| El Sol | Maricopa County | 50 | 200 | 2024 |
| Foothills I | Yuma County | 17.5 | 52.5 | 2023 |
| Foothills II | Yuma County | 17.5 | 52.5 | 2023 |
| Gila Bend I | Maricopa County | 16 | 48 | 2023 |
| Gila Bend II | Maricopa County | 16 | 48 | 2023 |
| Paloma | Maricopa County | 17 | 51 | 2023 |
| Hyder I | Yuma County | 16 | 48 | 2023 |
| Hyder II | Yuma County | 14 | 42 | 2023 |
| Yuma Storage | Yuma County | 70 | 280 | 2024 |
The ten operational projects total 191MW/623MWh while Yuma Storage, the largest single project at 70MW/280MWh, will increase that total by around one-third, leading to a total operational portfolio of 261MW/903MWh.
The firm also has operational and under-construction BESS projects in Illinois, Wisconsin, West Virginia, New York, and Iowa, with 20 in total listed on its website across all states and stages.
Arizona has quickly become one of the most active grid-scale BESS markets in the US after California and Texas. In the past month, utility Tucson Electric Power announced it would build a second 200MW/800MWh project in the state, while Salt River Project (SRP) signed an offtake agreement for a 250MW/1,000MWh system, with both systems set to come online in 2026.
