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Great Britain · the operating fleet

Dollymans Storage

102 MW, about 204 MWh (2 hours, from the capacity market de-rating class) in Essex and Kent. Everything on this page is read from published data for the 364 days to 16 October 2026, or is labelled as an estimate.

What it is

Registered power102 MW balancing mechanism registration
Storage duration2 hours capacity market de-rating class
Charging zoneEssex and Kent
Connection siteRochford
PostcodeSS11 8UA
Balancing mechanism unitE_DOLLB-1

Who owns it and who trades it

Traded byDollymans Storage Limitedconfirmed, Elexon's register
Owned byDOLLYMANS STORAGE LIMITED
Owner established fromcapacity market registered holder
UltimatelyStatera Energy confirmed source

How we know. Statera's own page for each project names Statera Energy as both project developer and project owner.

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 is built from

Battery systemSungrow, air cooled
CellsCATL claimed for the augmentation units (a mapper's survey note, unverified)
Power conversionSungrow (MV skids and PCS units)
Engineering and constructionStatera Energy Projects (in house); Ethical Power, M&E balance of plant for the grid connection; Impact Formwork & Civils, reinforced concrete foundations, plinths and transformer bases
Entered operation2023-06 (energisation)
Connection voltage132 kV documented: 0.3 km 132 kV cable to Rayleigh UKPN substation, iDNO teed connectio

From published documents, not from any register: supplier and contractor project pages, owner announcements and the trade press. Confidence: confirmed (build); possible (augmentation). Checked 2026-08-30. source 1 · source 2. Fields not shown are not published anywhere we have found, and we do not guess them.

What it earned

Line364 days to 16 October 2026
Balancing mechanism£2.9m
Response and reserve auctions auction implied£636k
Capacity market£1.5m
Three lines together£5.1m

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 10,804 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 11 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. 359 days to 11 October 2026, 45 of them still provisional in Elexon's settlement runs. Method and caveats

LineMWh or £
Metered export, what crossed the meter out65,494 MWh
Metered import, what crossed the meter in76,391 MWh
Equivalent full cycles, everything sent out over one full charge321 over 359 days, 326 a year at that rate
Apparent meter to meter efficiency86%, an ordinary battery: round trip losses alone
Balancing offers accepted43,474 MWh
Balancing bids accepted27,225 MWh
Position outside balancing, export62,294 MWh
Position outside balancing, import89,440 MWh
Of which expected response delivery, net−16,647 MWh 7,385 out, 24,032 in
Traded position, net−10,499 MWh 65,988 out, 76,487 in
Traded position at the market index, sold£8.1m
Traded position at the market index, bought£6.0m
Traded position, net, at the index£2.0m
Response delivery, net, at the imbalance price−£2.0m −£1.8m at the index
Balancing and outside balancing together£2.8m £28.38/kW/yr

When it moved, against when power was dear

Across every half hour this unit was metered the market index averaged £97.34. What it sent out was worth £122.07 a megawatt hour at that same index, 1.25 times the average. What it took in was worth £78.63, 0.81 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 27,225 MWh of accepted bids it paid an average of £80.56 a megawatt hour. The market index averaged £109.24 across those same half hours, so it bought back at £28.68 a megawatt hour below the going price.

Price it paidVolumeAverageCash
below zero1,967 MWh−£24.60£48k received
£0 to £251,826 MWh£12.59£23k
£25 to £501,578 MWh£38.61£61k
£50 to £753,510 MWh£64.91£228k
£75 to £1009,164 MWh£87.74£804k
above £1009,180 MWh£122.64£1.1m

On 1,967 MWh the price was below zero: NESO paid this unit an average of £24.60 a megawatt hour to take energy, £48k in all. That is a constrained network with more generation on it than it can move.

The other direction, offers, is much smaller here: 43,474 MWh where NESO asked for more, paid at an average of £114.11 against an index of £80.53.

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/yr70th percentile100 units
Balancing incomeEngland and Wales peer group58th percentile72 units
Balancing income2.0 hour duration cohort59th percentile64 units
All three measured lineswhole fleet, £/kW/yr78th percentile230 units
Energy sent outhours at full power72nd percentile98 units
Energy taken inhours at full power53rd percentile98 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
Thurrock Flexible (THURB-1)1002h£76.9/kW/yr
Dollymans Storagethis battery1022h£49.7/kW/yr
Thurrock Flexible (THURB-3)1001.7h£48.8/kW/yr
Lakeside BESS1052h£38.2/kW/yr
Ferrybridge BESS BMU-1762h£35.3/kW/yr
KXP Immingham BESS812h£12.5/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.