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Great Britain · the operating fleet

Holes Bay Battery

7 MW, about 14 MWh (2 hours, from the capacity market de-rating class) in Somerset and Wessex. Everything on this page is read from published data for the 364 days to 11 November 2026, or is labelled as an estimate.

What it is

Registered power7 MW balancing mechanism registration
Storage duration2 hours capacity market de-rating class
Charging zoneSomerset and Wessex
Connection siteHoles Bay, Poole
PostcodeBH15
Balancing mechanism unitE_BHOLB-1

Who owns it and who trades it

Traded byTesla Motors Limitedruns several sitesconfirmed, Elexon's register
Owned byHARMONY HB LIMITED
Owner established fromcapacity market registered holder
UltimatelyFRV (Abdul Latif Jameel) confirmed source

How we know. The control filing shows FRV Solar Holdings XVIII S.L., the Spanish holding company of Fotowatio Renewable Ventures, entering in November 2019 and handing straight on to the individual who controls the Abdul Latif Jameel group, who holds more than half the shares and appoints the directors.

Market registers name the party that sells into the market, which for a battery is usually an optimiser under contract rather than the owner. Elexon's balancing mechanism unit register names the seller here and the name is checked against it on every build. How we tell them apart

What it earned

Line364 days to 11 November 2026
Balancing mechanism£97k
Response and reserve auctions auction implied£75k
Capacity market£116k
Three lines together£288k

Balancing is offer revenue and does not net off the cost of the power. The response and reserve figure is the value implied by the published auction results, award quantity times clearing price times the length of the delivery window, and not a settled payment. Capacity market income is the cleared price raised for inflation where the auction set a base period, split by month on EMRS's weights. Method

Outside the balancing mechanism, derived from the meter

Elexon publishes what this unit's meter recorded every half hour. Take away the balancing volumes NESO accepted and what is left is the position the unit ran outside the balancing mechanism: its wholesale trading, its frequency response delivery, and its losses, together. This unit held a frequency response contract in 9,182 of those half hours. The energy the contract asked of it, contracted megawatts times NESO's published delivery curve at the measured grid frequency, is taken out of the position and valued at the imbalance price, because it sits outside the unit's declared position and that is the price Elexon settles it at. What remains is the traded position, valued at the market index. In 9 half hours a contract was held but the grid frequency is not yet held, so those are left in the traded position. The volumes are measured. The prices are public benchmarks, not this unit's trades. The product is derived, and is shown apart from the three measured lines above. 358 days to 5 November 2026, 42 of them still provisional in Elexon's settlement runs. Method and caveats

LineMWh or £
Metered export, what crossed the meter out5,935 MWh
Metered import, what crossed the meter in7,041 MWh
Equivalent full cycles, everything sent out over one full charge418 over 358 days, 426 a year at that rate
Apparent meter to meter efficiency84%, an ordinary battery: round trip losses alone
Balancing offers accepted3,347 MWh
Balancing bids accepted3,599 MWh
Position outside balancing, export5,034 MWh
Position outside balancing, import5,888 MWh
Of which expected response delivery, net−1,171 MWh 244 out, 1,415 in
Traded position, net317 MWh 5,113 out, 4,796 in
Traded position at the market index, sold£629k
Traded position at the market index, bought£389k
Traded position, net, at the index£240k
Response delivery, net, at the imbalance price−£124k −£119k at the index
Balancing and outside balancing together£222k £31.81/kW/yr

This battery connects to a distribution network. For such a unit the volumes Elexon publishes are settlement volumes: the site's own meter multiplied by the network operator's line loss factor for that half hour. The factor is usually within a few per cent of one, so the megawatt hours, cycles and efficiency above can sit a little above or below what crossed the site's meter. The money is settled on the same adjusted volumes. Method and caveats

When it moved, against when power was dear

Across every half hour this unit was metered the market index averaged £104.66. What it sent out was worth £123.03 a megawatt hour at that same index, 1.18 times the average. What it took in was worth £81.16, 0.78 times. Selling above one and buying below one is a unit positioned into the dear half hours and out of the cheap ones. It measures the half hours it chose, not the price anyone paid it, which is not published.

What it paid to buy energy back

When NESO accepts a bid, this unit delivers less than it had already sold, or takes more in. It pays for the energy it no longer delivers, and that payment is most of what makes the balancing figure above negative. Whether that is a cost or a margin depends on the price it paid. Across 3,599 MWh of accepted bids it paid an average of £81.68 a megawatt hour. The market index averaged £104.42 across those same half hours, so it bought back at £22.74 a megawatt hour below the going price.

Price it paidVolumeAverageCash
below zero137 MWh−£16.62£2k received
£0 to £25137 MWh£13.67£2k
£25 to £50189 MWh£38.95£7k
£50 to £75834 MWh£64.87£54k
£75 to £1001,344 MWh£87.63£118k
above £100958 MWh£120.22£115k

On 137 MWh the price was below zero: NESO paid this unit an average of £16.62 a megawatt hour to take energy, £2k in all. That is a constrained network with more generation on it than it can move.

The other direction, offers, is much smaller here: 3,347 MWh where NESO asked for more, paid at an average of £119.45 against an index of £87.11.

Physical checks passed: the meter never exceeded the registered power by more than fifteen per cent, and the year's exports against imports are what a battery does.

Where it stands

Balancing incomewhole fleet, £/kW/yr75th percentile103 units
Balancing incomeEngland and Wales peer group65th percentile75 units
Balancing income2.0 hour duration cohort65th percentile63 units
Balancing incomebatteries sold by Tesla Motors Limited43rd percentile15 units
All three measured lineswhole fleet, £/kW/yr85th percentile234 units
Energy sent outhours at full power77th percentile101 units
Energy taken inhours at full power80th percentile101 units

Percentiles, so 90 means better than nine in ten of the cohort named beside it, on that measure alone, over the same 364 days. Rates are pounds per kilowatt per year, annualised over the days the unit has been on the system, the same figures the performance league ranks on. A high position in the taken-in table is not a fault: a constraint asset is paid to charge, and charging is its job.

The nearest comparables

The five nearest in size in England and Wales, and this battery among them, ranked by what each was paid for every kilowatt it holds over the 364 days to the same date. They run for about the same length of time. Same market, same rules, same weather.

BatteryMWHoursMeasured, per kW
Holes Bay Batterythis battery72h£40.6/kW/yr
Conrad (MIDSOMER)52h£28.3/kW/yr
Broadditch Battery112h£26.5/kW/yr
Gridbeyond32h£19.5/kW/yr
Nevendon102h£13.1/kW/yr
Ecotricity (SMART GRID)92h£11.0/kW/yr

See it on the map

Open the operating map here

Every figure on this page traces to a published file. If something here is wrong about your asset, the methods section says how to tell us.

Need every battery at once? The register is not offered for automated download, and bulk access is by request at hello@vitreouslabs.com.