Return closes €180 million financing and tolling agreement for 200 MW / 800 MWh Sirius battery energy storage project in the Netherlands with Vattenfall

Type: Financing · Technology: Storage · Country: Netherlands · Capacity: 200 MW · Value: EUR 180M · Announced: 2026-09-01

Return reached financial close on the 200 MW / 800 MWh Sirius battery energy storage system (BESS) in Winschoten, Groningen, Netherlands, securing €180 million in financing through its battery portfolio framework. The project, with commercial operations scheduled to begin in Q4 2027, features a four-hour battery system and represents the largest fixed-price battery storage tolling contract signed in the Netherlands to date. Under the long-term tolling agreement, Vattenfall will pay a fixed fee for access to Sirius’s charging, storage, and power delivery capacity, determining when the battery charges and discharges to manage renewable generation and its customer portfolio. The financing was provided by a lending group comprising ING, NatWest, Deutsche Bank, ABN AMRO, and Rabobank, while Sirius will connect to TenneT’s Meeden substation under a Time-Dependent Transmission Rights agreement requiring grid-adaptive charging and discharging. The project builds on an existing 2025 agreement between Return and Vattenfall, which covered 50 MW of the 100 MW / 200 MWh Antares BESS project in Waddinxveen, and involves technology supply from Huawei, Hanab, and Omexom for battery systems, construction, and installation.

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