Brentwood

Part of Brentwood, one of 2 balancing units at one site totalling 101 MW. This page is the E_BRETB-1 unit alone.

This registration has been superseded. The battery here has sold as Brentwood BESS since 17 March 2026; this code, sold by ARENKO CLEANTECH LIMITED, last appeared on 8 December 2025. The page stays for the record, and the unit is no longer counted in fleet totals or ranked in the league.

What it is

Who owns it and who trades it

How we know. Voltwise's own project list carries Brook Farm and Brentwood; acquired with the SMS battery business, announced 23 June 2025.

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 1,173 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 3 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. 125 days to 17 March 2026. 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 £85.13. What it sent out was worth £93.80 a megawatt hour at that same index, 1.10 times the average. What it took in was worth £75.97, 0.89 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.

Checks this unit did not pass cleanly. Published anyway, because a flagged figure with its flag is more use than a blank.

• only 125 of 364 days metered

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. How long this battery can run for is not published, so duration is not used to choose them. Same market, same rules, same weather.

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.