EDP Renewables has signed a tolling agreement with Salt River Project for a 200 MW battery in Arizona. Batteries in Arizona are not new, and neither are utility contracts for them. What stands out is the length. Every other Arizona utility battery contract on Enerdatics' record runs 20 years. This one runs 24.
Key takeaways
- EDP Renewables North America signed a 24-year tolling agreement with Salt River Project (SRP) for a 200 MW, 800 MWh battery energy storage system in Arizona, announced on 23 July 2024.
- The 200 MW SRP battery was described as EDPR's largest battery storage installation in North America at the time of the agreement.
- Enerdatics records seven other utility battery contracts in Arizona announced in 2023 and 2024 with Arizona Public Service or SRP that disclose a term, and all seven run for 20 years.
- Of 49 US battery offtake contracts announced in 2023 and 2024 with a disclosed term, Enerdatics records only three running 24 years or longer: EDPR's SRP toll, NextEra's 24.5-year Northern Divide contract with Basin Electric and Hydrostor's 25-year Willow Rock contract.
- Enerdatics has identified the 200 MW, 800 MWh Flatland BESS, supplying SRP under a 24-year tolling agreement, as likely part of the 1.6 GW EDPR portfolio in which Ares Management bought a 49 percent stake in October 2025.
What is a tolling agreement for a battery?
It is a contract in which the buyer rents the battery's capability rather than buying its output. Under a toll, the utility pays the owner a regular payment for keeping the battery available, and the utility decides when it charges and discharges. The owner's job is to keep the system working to specification.
That allocation matters for how the asset is valued. A merchant battery earns money by buying power cheaply and selling it when prices spike, which makes its revenue depend on market volatility. A tolled battery earns a contracted payment instead. The trading upside and the trading risk both pass to the utility.
For SRP, a 200 MW, four-hour battery is a tool for moving midday solar output into the evening peak. Duration is the energy capacity divided by the power rating, so 800 MWh behind 200 MW gives four hours of full output.
Why does a 24-year term stand out?
Because the Arizona market has settled on 20 years. Enerdatics records seven other battery contracts signed by Arizona Public Service and SRP over 2023 and 2024 with a disclosed term, including SRP's own 250 MW Pediment tolling agreement with Aypa Power, announced five days before EDPR's. Every one of them runs 20 years.
A 24-year contract asks the owner to keep the battery performing to specification for four more years than its peers, which usually means planning for augmentation, the addition or replacement of battery modules over time to keep the system delivering its rated capacity.
The extra four years are worth having for the owner. They add a fifth to the contracted revenue period and push the point at which the battery becomes a merchant asset further into the future. For a buyer of the project, a longer contract means more years of predictable cash flow to value.
Who ended up owning the battery?
EDPR still controls it, but not alone. In October 2025, EDPR sold a 49 percent stake in a 1.6 GW US portfolio to a fund managed by Ares Management's Infrastructure Opportunities strategy. The deal carried an enterprise value of about $1.42 billion on a 49 percent basis, valuing the whole portfolio at $2.9 billion, and Leap links the SRP tolling agreement to that transaction.
The portfolio comprises 1,030 MW of solar, 402 MW of wind and 200 MW of storage across ten projects. Enerdatics has identified the Flatland BESS, a 200 MW, 800 MWh battery supplying SRP under a 24-year tolling agreement, as likely part of it. Leap's project record now shows Flatland owned 51 percent by EDP Renewables and 49 percent by Ares, with SRP as offtaker, and it reached commercial operations in June 2026.
The contract length helps explain why the battery belongs in a portfolio built for a long-term investor. EDPR reported an average remaining contract duration of 18 years across the portfolio. Flatland's 24-year toll sits well above that average and stretches the contracted life of the whole package.
Enerdatics' data shows how rare that length is nationally. Of 59 US battery offtake contracts announced in 2023 and 2024 in Leap, 49 disclose a term. Twenty run 15 years and 20 run 20 years. Only three reach 24 years or more: the EDPR and SRP toll, NextEra's 24.5-year contract with Basin Electric for the Northern Divide battery and Hydrostor's 25-year contract with Central Coast Community Energy for Willow Rock.
What does the deal signal for Arizona storage?
It signals that Arizona utilities are willing to contract for storage on terms closer to the life of a generation asset than to that of a piece of equipment. SRP signed two large tolling agreements within a week in July 2024. One followed the market's 20-year norm and the other went four years further.
It also shows how utility contracts feed asset rotation, the practice of building projects, selling minority stakes once they are contracted and recycling the proceeds into new development. EDPR has done this before in the US, including its sale of 80 percent of three operating solar parks to Plenitude. The Ares portfolio also includes the 110 MW Hickory solar project, which sells to Microsoft under a 15-year agreement. A 24-year battery toll is the longest-dated contract in that mix.
Finally, it points to a widening range of battery contract structures in the US West. Idaho Power's 20-year battery contract with Prevalon was signed with the equipment supplier rather than a developer. SRP's contract with EDPR shows the other lever buyers can pull: time.
Frequently asked questions
How long is EDPR's tolling agreement with Salt River Project? The tolling agreement between EDP Renewables North America and Salt River Project for the 200 MW, 800 MWh Arizona battery runs for 24 years. It was announced on 23 July 2024.
How does the EDPR and SRP contract compare with other Arizona battery deals? Enerdatics records seven other Arizona utility battery contracts announced in 2023 and 2024 with a disclosed term, signed with Arizona Public Service or SRP. All seven run 20 years.
Is the SRP battery part of EDPR's sale to Ares Management? Enerdatics has identified the 200 MW Flatland BESS, which supplies SRP under a 24-year toll, as likely part of the 1.6 GW portfolio in which Ares bought a 49 percent stake in October 2025. Leap lists Flatland as 51 percent EDPR and 49 percent Ares.
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