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Great Britain · the operating fleet

SSE Salisbury

49 MW, about 98 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 16 October 2026, or is labelled as an estimate.

What it is

Registered power49 MW response and reserve auction registration
Storage duration2 hours capacity market de-rating class
Charging zoneSomerset and Wessex
Connection siteWiltshire
PostcodeSP2 0BL
Balancing mechanism unit2__HIMPO002 a supplier unit registered by the company that trades it; its balancing actions are counted on this page

Who owns it and who trades it

Traded bySSE ENERGY SUPPLY LIMITEDconfirmed, Elexon's register
Owned bySSE BATTERY SALISBURY LIMITED
Owner established fromcapacity market registered holder
UltimatelySSE confirmed source

How we know. SSE's own battery storage pages.

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 systemWärtsilä
Entered operation2024-04 (full operations; first auction in our archive 8 April 2024 agrees)
Container count26 battery units

From published documents, not from any register: supplier and contractor project pages, owner announcements and the trade press. Confidence: confirmed. Checked 2026-08-31. source 1. 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£1.8m
Response and reserve auctions auction implied£417k
Capacity market£747k
Three lines together£3.0m

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 4,006 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. 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 out37,521 MWh
Metered import, what crossed the meter in45,289 MWh
Equivalent full cycles, everything sent out over one full charge383 over 359 days, 389 a year at that rate
Apparent meter to meter efficiency83%, plausible: losses plus a standing load that is material against a modest throughput
Balancing offers accepted22,677 MWh
Balancing bids accepted9,134 MWh
Position outside balancing, export30,244 MWh
Position outside balancing, import51,555 MWh
Of which expected response delivery, net−340 MWh 3,664 out, 4,004 in
Traded position, net−20,972 MWh 28,413 out, 49,385 in
Traded position at the market index, sold£3.6m
Traded position at the market index, bought£3.7m
Traded position, net, at the index−£97k
Response delivery, net, at the imbalance price−£49k −£29k at the index
Balancing and outside balancing together£1.6m £33.80/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 £127.80 a megawatt hour at that same index, 1.31 times the average. What it took in was worth £75.48, 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 9,134 MWh of accepted bids it paid an average of £73.85 a megawatt hour. The market index averaged £105.44 across those same half hours, so it bought back at £31.59 a megawatt hour below the going price.

Price it paidVolumeAverageCash
below zero412 MWh−£23.34£10k received
£0 to £25485 MWh£12.21£6k
£25 to £501,424 MWh£38.30£55k
£50 to £752,040 MWh£63.90£130k
£75 to £1002,870 MWh£86.25£248k
above £1001,902 MWh£129.23£246k

On 412 MWh the price was below zero: NESO paid this unit an average of £23.34 a megawatt hour to take energy, £10k in all. That is a constrained network with more generation on it than it can move.

The other direction, offers, is much smaller here: 22,677 MWh where NESO asked for more, paid at an average of £108.00 against an index of £75.74.

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

All three measured lineswhole fleet, £/kW/yr81st percentile230 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
Melksham East492h£132.1/kW/yr
York492h£61.7/kW/yr
SSE Salisburythis battery492h£60.7/kW/yr
Swangate492h£57.1/kW/yr
Melksham West492h£46.2/kW/yr
Cowley491.5h£30.5/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.