Varco Energy and Fluence Energy UK Ltd. have announced the successful commercial launch of Phase 1 of the Sizing John Battery Energy Storage System (BESS), marking a key milestone in strengthening the UK’s renewable-ready grid infrastructure. The first phase, a 57 MW / 137.5 MWh installation, is now fully operational within the Mersey Ring east of Liverpool—one of the country’s most grid-constrained regions.
Alongside this achievement, Varco has initiated Phase 2, selecting Fluence to expand the project by an additional 85.5 MW / 201 MWh. Once completed, the combined 142.5 MW / 348.5 MWh system will position Sizing John among the largest BESS projects in the UK, significantly enhancing regional energy resilience.
Phase 1 employs Fluence’s Gridstack solution, providing long-duration storage with a 2.4-hour discharge capability—one of the longest durations currently operational in the country. The system is expected to reduce local grid congestion, stabilize prices, and support growing renewable penetration.
Phase 2, targeted for commercial operation in Q4 2026, will integrate the next-generation Gridstack Pro 5000, equipped with advanced grid-forming capabilities. This technology enables active control of voltage and frequency, a critical function highlighted by recent widespread events such as the Iberian blackout, underscoring the need for systems that can support grid stability without relying on traditional synchronous power sources.
Varco Energy Director Richard Whitmore said the project demonstrates the company’s commitment to grid innovation, adding that the grid-forming expansion will “set a new standard for regional stability.” Brian Perusse, Managing Director, UK & Ireland at Fluence, highlighted that Sizing John will help advance longer-duration storage and enhance the UK’s transition toward a net-zero power system.
This marks Varco Energy’s second BESS project to enter full operations following the Native River BESS in April 2025. The company plans to energize 250 MW of additional projects within 18 months, supported by a further 275 MW pipeline under the Adaptogen Capital Battery Storage Fund.
By enabling renewable integration and stabilizing the UK grid, Varco and Fluence’s collaboration is set to play a pivotal role in delivering accessible, reliable, and affordable clean energy.
