BW ESS
Owns 4 batteries at 4 sites, 400 MW, which is 4.8 per cent of everything operating in Great Britain. It sells none of that power itself. The register names one seller for the whole fleet, Welbar Energy Storage Limited.
Who sells its power
The balancing mechanism register names the company allowed to sell each unit's power. That company is usually an optimiser or a supplier working under contract, which is why the registers cannot answer the ownership question on their own. Where the seller is one of the owner's own companies, the row says so.
| Seller | Batteries | MW | Of this fleet |
|---|---|---|---|
| Welbar Energy Storage Limited | 4 | 400 | 100% |
What it was paid
The three published lines, added up across the fleet for the 364 days to 6 November 2026. Wholesale trading income is invisible for every owner, not just this one, and nothing here nets the cost of charging. The rate is per kilowatt of current capacity.
| Balancing mechanism, paid to discharge | £295k |
| Balancing mechanism, paid out to charge | −£937k |
| Response and reserve auctions | £64k |
| Capacity market | £236k |
| Income across the fleet, per kilowatt | £1.49/kW/yr fleet 45.50 |
| Median battery, all three lines | £1.07/kW/yr |
| Hours at full power, sent out | 3 h/yr |
| Hours at full power, taken in | 13 h/yr |
What the fleet is made of
Duration, by megawatt
Region, by megawatt
Every battery it owns
| Battery | MW | Sold by | Grade | £/kW/yr |
|---|---|---|---|---|
| Hams Hall (HAMHB-1) Mid Wales and The Midlands | 100 | Welbar Energy Storage Limited | confirmed | 3.52 |
| Hams Hall (HAMHB-3) Mid Wales and The Midlands | 100 | Welbar Energy Storage Limited | confirmed | 0.86 |
| Hams Hall (HAMHB-4) Mid Wales and The Midlands | 100 | Welbar Energy Storage Limited | confirmed | 0.39 |
| Hams Hall (HAMHB-2) Mid Wales and The Midlands | 100 | Welbar Energy Storage Limited | confirmed | 1.07 |
How we know
Confirmed means a control filing at Companies House, or the owner's own published statement, names the company. Probable means the evidence is strong and indirect. Named means the register leaves the owner blank, the balancing code carries the owner's initials, and a sibling unit at the same site is already settled. Each chain below is printed once, with the batteries it settles.
Confirmed Hams Hall (HAMHB-1), Hams Hall (HAMHB-3), Hams Hall (HAMHB-4), Hams Hall (HAMHB-2)
Welbar Energy Storage Limited is the lead party of all four units, holds the 399.9 MW connection at Hams Hall in the connection register and holds the capacity market agreement HAMS26 at the site. The developer register resolves the company to BW ESS; the planning database names it with Penso Power. Source
Attribution. A battery belongs to whoever the documents name today, so a fleet that changed hands during the year credits the whole year to the current owner. Groups are joined only where a filing joins them; a company that holds through several vehicles appears once, under the name at the top of the chain. Directors and registered offices are never used as evidence on their own. Why the registers cannot answer this question