Varco Energy has brought Phase 1 of the 57 MW / 137.5 MWh Sizing John BESS in the UK into full commercial operation with Fluence, while Phase 2 is underway to expand the site to 142.5 MW / 348.5 MWh. The two-phase project is designed to deliver longer-duration storage, grid-forming capability, and support for congestion management, price stability, and renewable integration, with Phase 2 scheduled for completion in Q4 2026.
DATA SNAPSHOT
| Field | Value |
|---|---|
| Project | Sizing John BESS |
| Location | United Kingdom |
| Owner/Operator | Varco Energy |
| Capacity (Phase 1) | 57 MW / 137.5 MWh (2.4-hour) |
| Capacity (Phase 2) | 85.5 MW / 201 MWh |
| Total Capacity (Post-Phase 2) | 142.5 MW / 348.5 MWh |
| Technology Provider | Fluence Energy UK Ltd. |
| Financing | Adaptogen Capital Battery Storage Fund |
| Platform | Fluence Gridstack (Phase 1) |
| Platform | Gridstack Pro 5000 (Phase 2) |
| Phase 2 COD | Q4 2026 |
UK-based battery storage asset owner and operator Varco Energy, financed by the Adaptogen Capital Battery Storage Fund, together with Fluence Energy UK Ltd., a subsidiary of Fluence Energy, Inc., has confirmed that Phase 1 of the 57 MW / 137.5 MWh Sizing John Battery Energy Storage System has entered full commercial operation.
Varco Energy has also initiated Phase 2 of the project and appointed Fluence to deliver an additional 85.5 MW / 201 MWh of capacity, increasing the site’s total scale to 142.5 MW / 348.5 MWh. Following energisation of Phase 2, the Sizing John facility is expected to be among the UK’s largest battery energy storage systems by installed capacity.
The Sizing John project has been structured as a two-phase development to provide both near-term and longer-term system support. Phase 1 feature a 2.4 hours, placing it among the longer-duration operational battery projects in the UK. This configuration allows the system to respond to regional congestion and mitigate price volatility associated with increasing levels of variable renewable generation.
The system operates using Fluence’s Gridstack platform, enabling energy shifting and local supply-demand balancing. Technology for the project has been supplied by Fluence Energy through its UK subsidiary, with Phase 1 configured for operational reliability and longer-duration discharge during peak demand and congestion periods.
Construction of Phase 2 has commenced and will expand the site by an additional 85.5 MW / 201 MWh. Once energised, the combined facility will reach 142.5 MW / 348.5 MWh, positioning Sizing John among the largest battery energy storage projects in the UK by installed capacity. Phase 2 incorporates Fluence’s next-generation Gridstack Pro 5000 technology and is scheduled to be enter commercial operations in Q4 2026 and will deploy.
Richard Whitmore, Director at Varco Energy, said that the commissioning of Phase 1 and the launch of Phase 2 reflect the project’s focus on addressing grid constraints, with grid-forming capabilities intended to support regional voltage and frequency stability following recent system disturbance events in Europe.
Brian Perusse, Managing Director for UK and Ireland at Fluence, said that the completion of Phase 1 and progression of Phase 2 demonstrate the delivery of longer-duration storage and grid-forming capabilities intended to support grid stability and renewable integration in the UK market.
The Sizing John project forms part of Varco Energy’s UK portfolio expansion. Following the commissioning of the Native River BESS in April 2025, the company plans to energize around 250 MW of additional battery capacity over the next eighteen months, with a further 275 MW in development across constrained grid regions. The projects are designed to support renewable generation integration and contribute to grid balancing across the UK electricity system.