Constantine Energy Storage
Owns 2 batteries at 2 sites, 115 MW, which is 1.7 per cent of everything operating in Great Britain. It sells none of that power itself. The register names 2 other companies as the sellers: HD143OCK Ltd and HD777FRY Ltd.
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 |
|---|---|---|---|
| HD143OCK Ltd | 1 | 58 | 50% |
| HD777FRY Ltd | 1 | 57 | 50% |
What it was paid
The three published lines, added up across the fleet for the 364 days to 6 September 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 | £7.9m |
| Balancing mechanism, paid out to charge | −£3.4m |
| Response and reserve auctions | £215k |
| Capacity market | £1.3m |
| Income across the fleet, per kilowatt | £81.62/kW/yr fleet 35.48 |
| Median battery, all three lines | £101.54/kW/yr |
| Hours at full power, sent out | 652 h/yr |
| Hours at full power, taken in | 403 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 |
|---|---|---|---|---|
| Ocker Hill Mid Wales and The Midlands | 58 | HD143OCK Ltd | confirmed | 101.54 |
| Monk Fryston South Lancashire, Yorkshire and Humber | 57 | HD777FRY Ltd | confirmed | 61.36 |
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 Ocker Hill, Monk Fryston
The project companies are named HD, a number and three letters of the place, so FRY is Monk Fryston and OCK is Ocker Hill. Both are controlled by Constantine Energy Storage Midco LLP, which is controlled by Constantine Energy Storage LLP. Above that the register carries a statement that there is no registrable person, so who owns Constantine is not published anywhere we can read. Both companies were held by Pelagic Energy Development Ltd from 2019 until 2025. 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