Loudwater

What it is

The power on this page comes from the owner. Eku Energy, which built the battery, gave Loudwater near High Wycombe as 39 MW with 55 MWh of storage when it was fully commissioned in August 2025, in an announcement quoting its chief executive (Energy-pedia, 6 August 2025). Elexon registers the unit at 33 MW. The meter agrees with the builder: across 21,310 half hours from 1 August 2025 to 18 October 2026 it averaged more than 33 MW sending power out in 109 of them, up to 39.5 MW, and up to 40.2 MW taking it in, which a 33 MW battery cannot do. Every per kilowatt figure on this site is worked from 39 MW. Read the announcement.

Where the duration comes from. Eku Energy, which built the battery, gave Loudwater as 39 MW with 55 MWh of storage when it was commissioned in August 2025 (Energy-pedia, 6 August 2025, energy-pedia.com), about 1.4 hours. Until 25 October 2026 this page gave 1 hour from the capacity market class on the registered 33 MW, so 33 MWh. The meter agrees with the builder: in the year to 18 October 2026 the battery sent out between 50 and 57 MWh in a single unbroken discharge 27 times. One discharge, on 23 July 2026, came to 64 MWh, more than 55 MWh allows; it rests on Elexon's first settlement run, which is often revised, so it is not used. What the battery declares to NESO is lower, 44 MWh in the fullest 5% of 541 half hours from 13 to 24 October 2026, and a declaration can only show the least a battery holds. Every megawatt hour figure on this site for this battery is worked from 1.4 hours.

Who owns it and who trades it

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

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 7,654 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 7 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

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 £129.28 a megawatt hour at that same index, 1.24 times the average. What it took in was worth £86.87, 0.83 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 8,311 MWh of accepted bids it paid an average of £80.60 a megawatt hour. The market index averaged £110.33 across those same half hours, so it bought back at £29.73 a megawatt hour below the going price.

On 612 MWh the price was below zero: NESO paid this unit an average of £22.46 a megawatt hour to take energy, £14k in all. That is a constrained network with more generation on it than it can move.

The other direction, offers, is much smaller here: 14,209 MWh where NESO asked for more, paid at an average of £120.73 against an index of £87.16.

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

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.

In its distribution register

The distribution register of Scottish and Southern Electricity Networks lists this site as LOUDWATER, 40 MW, connected on 30 January 2025. Matched on a site word in common, 0 km apart.

See it on the Development Atlas

From each operator’s embedded capacity register, read every Monday. How the registers are linked to the units that trade.

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.