About 1,121 MW of batteries are running that no market register can see
Every balancing dataset published in Great Britain describes the batteries that register in the markets it covers. That is not the fleet. Reading owners' own project lists, supplier case studies and financing announcements against the registers, we have so far named 19 operating or near-operating batteries, about 1,121 MW, that appear in none of them. Each is listed here with what its owner or supplier has published, the document, and the mechanism that hides it. A site on this list is not a rumour: it is a battery somebody has announced, financed or energised, and that the public record of the markets cannot see.
Inside another company's identity: 3 sites, 228 MW
The battery trades under a supplier or aggregator's own registration, so nothing public carries its name. A toll or an offtake makes the counterparty the seller.
| Site | MW | What is published |
|---|---|---|
| Bramley | 100 | 331 MWh; 2025-02-17; owner: Penso Power and BW ESS; sells through: Shell Energy, seven year fixed price toll from August 2024, the UK's first single asset BESS tolling agreement; built with: Sungrow, PowerTitan 2.0 (grid forming, AC DC block) confirmed source 1 source 2 |
| Minety | 100 | 136 MWh; 2021; owner: China Huaneng Group and CNIC Corporation (Chinese state backed), who acquired the project; Penso Power and BW ESS association applies to the extension plans; sells through: Shell Energy Europe holds the offtake (signed February 2020); its subsidiary Limejump optimises and trades, including Dynamic Containment; built with: Sungrow confirmed source 1 source 2 |
| Basildon BESS, Eku Basildon, Essex | 28 | 56 MWh; operational per Eku's project list; owner: Eku Energy; sells through: Habitat Energy optimises (ledger); NHOA supplied; built with: NHOA Energy (two Eku southern England projects, 130 MWh together) confirmed (site, operation); possible (truly unseen) source 1 |
Behind a generator unit: 2 sites, 70 MW
The battery charges and discharges inside a wind farm's own balancing unit. The tell is a registered demand capacity far larger than a wind farm needs for its own auxiliaries: Harestanes carries 51 MW where ScottishPower's other wind farms carry 2.5.
| Site | MW | What is published |
|---|---|---|
| Harestanes BESS Harestanes windfarm, Forest of Ae, Dumfries and Galloway | 50 | construction from July 2022; commissioning at the end of 2024; operations expected during 2025 (SPR 2024 accounts); owner: ScottishPower Renewables (Iberdrola) confirmed (existence, size, hosting unit); probable (operating date) source 1 source 2 |
| Battery@Ray, Ray wind farm, Northumberland | 20 | 45.5 MWh; energisation expected late 2022; owner: Vattenfall; sells through: Arenko, from November 2022 (its second co-located Vattenfall battery) confirmed (project); possible (truly unseen) source 1 |
Operating, no code joined: 7 sites, 416 MW
The owner says it operates and documents say it was built, but no auction or balancing code we hold joins to it. Some will be codes we have not yet joined; some are truly absent.
| Site | MW | What is published |
|---|---|---|
| Bumpers BESS Buckinghamshire | 99 | 198 MWh; 2023-10 (energised); owner: Harmony Energy Income Trust (HEIT), whose assets moved under Foresight; built with: Tesla, Megapack confirmed (site, size, operation); possible (truly unseen) source 1 source 2 |
| Low Carbon quartet: Meadow, Sandon Brook, Fern Brook, Birch | 95 | 190 MWh; first system online early 2025; owner: Low Carbon; sells through: Habitat Energy, Flexitricity and EDF on revenue share, with KrakenFlex as dispatch and controls across all four; built with: Trina Storage, 0.5P Elementa cabinets confirmed (portfolio); possible (which codes carry it) source 1 source 2 |
| Dunsinane, Dundee Dundee | 50 | 2023-04 (commercial operation); owner: SUSI Partners and Eelpower JV; sells through: EDF: market access and optimisation across balancing, trading and ancillary services confirmed (site, operation); possible (which code carries it) source 1 source 2 |
| Fordtown, Kintore near Aberdeen, serving SSEN and National Grid | 50 | owner: SUSI Partners and Eelpower JV; sells through: Habitat Energy, three year agreement with Eelpower on the Eel Dispatch platform (the Halesworth deal covers both sites) confirmed (site, deal); possible (truly unseen) source 1 |
| Sambar BESS, near Newquay near Newquay, Cornwall | 48 | 95 MWh; online targeted Q2 2025 (acquired by Varco April 2024); owner: Varco Energy (Adaptogen Capital); built with: GE Vernova: FlexIQ controls, FLEXinverter central inverters, battery DC blocks, with long term service confirmed (project); possible (operating and unseen, or still commissioning) source 1 |
| Loudwater BESS, Eku High Wycombe, Buckinghamshire | 40 | 55 MWh; operational per Eku's project list; owner: Eku Energy; sells through: Statkraft optimises (ledger); NHOA supplied; built with: NHOA Energy (two Eku southern England projects, 130 MWh together) confirmed (site, operation); possible (truly unseen) source 1 |
| Rusholme BESS near Selby, North Yorkshire | 35 | 70 MWh; 2023-10 (energised, announced alongside Bumpers); owner: Harmony Energy Income Trust (HEIT), whose assets moved under Foresight; built with: Tesla, Megapack confirmed (site, size, operation); possible (truly unseen) source 1 source 2 |
No register presence: 7 sites, 407 MW
Documented, operating, and absent from every register we read, with no explanation yet found.
| Site | MW | What is published |
|---|---|---|
| Minety South Storage and Minety South Storage 2 Minety, Wiltshire; two 50 MW sites beside Penso Power and BW ESS's 100 MW Minety, which is itself unseen | 100 | Minety South 2 entered commercial operations 7 November 2022 (Malmesbury); in the capacity market and Dynamic Containment; owner: Statera Energy confirmed (site exists, operational per the owner); possible (actually unseen rather than unjoined) source 1 source 2 |
| Bramford Pivot Power Bramford substation, Bullen Lane, Suffolk | 57 | 114 MWh; construction summer 2023, energisation targeted spring 2024; Wärtsilä lists it operational; owner: Pivot Power (EDF); sells through: EDF (Pivot Power appointed EDF to optimise its fleet); built with: Wärtsilä, GridSolv Quantum with GEMS confirmed (site, size, product); probable (operating today) source 1 source 2 |
| Overhill Pulse Clean Energy near Aberdeen | 50 | 110 MWh; full commercial operations targeted mid 2025; owner: Pulse Clean Energy (IMCO backed); built with: Powin, Stack750 with StackOS confirmed (project); probable (operating and unseen) source 1 |
| Pelham Storage Pelham substation area, Hertfordshire | 50 | listed operational on Statera's project page (no date given); owner: Statera Energy confirmed (site exists, operational per the owner); possible (actually unseen rather than unjoined) source 1 |
| Penwortham Storage Penwortham substation area, Lancashire | 50 | 50 MWh; 2024-05 (online; GRID's 25th operating asset); owner: Gresham House Energy Storage Fund plc (GRID) owns; Statera Energy developed and runs operations and maintenance confirmed (site, owner, dates); possible (which code carries it) source 1 source 2 |
| Creyke Beck Storage Creyke Beck substation, Cottingham, beside Harmony's Pillswood pair and Statera's own 50 MW Creyke Beck Power gas site | 50 | listed operational on Statera's project page (no date given); owner: Statera Energy confirmed (site exists, operational per the owner); possible (actually unseen rather than unjoined) source 1 |
| Ferrymuir Gore Street Fife, on the ScottishPower distribution network | 50 | activation Q4 2022, full commercial February 2023; owner: Gore Street confirmed (site); probable (unseen rather than under another code we hold) source 1 |
Why it matters
A fleet figure built from the registers alone undercounts what is running, and it undercounts unevenly: the tolled, the aggregated and the co-located are exactly the sites whose owners have chosen not to trade in their own name. Anyone benchmarking a battery against "the fleet" is benchmarking against the part of it that shows. The list grows as the register hunt continues, and a site leaves it the day a code joins to it.
From the technical register, checked 2026-08-31. The mechanism is read from the documents, not guessed; "no register presence" means we have found no explanation yet. Methods