Great Britain's batteries were paid £38 per kilowatt a year in August, on the lines anyone can measure
The measured floor of battery income: what the balancing mechanism, the response and reserve auctions and the capacity market actually paid the same 94 batteries, 3,589 MW, every month for a year, taken from published settlement and auction results and annualised the way the European indices are. Not a model of what a battery could have earned. Wholesale trading is left out because nobody publishes it, which is exactly why this is a floor.
Twelve months, one line, and the spread behind it
Pounds per kilowatt per year, each month annualised on its own days. The solid line is the whole panel weighted by size; the band holds the middle half of individual batteries; the dashed line is the median battery.
A stable panel: the 94 batteries with a balancing or auction record in both September 2025 and August 2026, superseded registrations removed, so the line moves with the market and not with arrivals. Balancing is the money paid to discharge; what a battery paid to charge through bids is not deducted, because the energy it bought is sold on in the wholesale market this page cannot see. Capacity market income is spread evenly across the days of the year; auction income is the value the published awards imply, not a settled payment.
The same year, by what kind of battery
| Cohort | Batteries | MW | £/kW/yr, year to 28 August 2026 |
|---|---|---|---|
| Nearer two hours (1.5 h and longer) | 45 | 2,031 | £60.2 |
| Nearer one hour (under 1.5 h) | 29 | 1,105 | £36.8 |
| Duration not published | 20 | 453 | £31.7 |
| England and Wales | 81 | 3,029 | £53.7 |
| Scotland | 13 | 561 | £26.4 paid to charge, not to discharge: the Scotland finding |
| Whole panel | 94 | 3,589 | £49.4 |
Duration is the capacity market de-rating class where a site holds an agreement, and our own measurement where it does not. The two duration rows and the not-published row add to the panel; so do the two geographic rows.
Month by month, the numbers behind the chart
| Month | Panel, £/kW/yr | Median battery | Middle half | Balancing | Auctions | Capacity market |
|---|---|---|---|---|---|---|
| Sep '25 | £49.9 | £50.8 | £29.3 to £76.5 | £5.2m | £7.6m | £2.0m |
| Oct | £57.8 | £56.4 | £35.2 to £79.9 | £7.0m | £8.6m | £2.1m |
| Nov | £54.2 | £48.1 | £27.8 to £67.2 | £7.2m | £6.8m | £2.0m |
| Dec | £41.4 | £30.3 | £19.0 to £53.7 | £6.3m | £4.2m | £2.1m |
| Jan '26 | £55.4 | £31.7 | £18.2 to £73.6 | £11.1m | £3.8m | £2.1m |
| Feb | £46.9 | £28.5 | £14.2 to £68.2 | £8.9m | £2.1m | £1.9m |
| Mar | £73.2 | £48.7 | £22.2 to £104.6 | £16.7m | £3.6m | £2.1m |
| Apr | £49.7 | £41.1 | £20.8 to £64.3 | £8.4m | £4.2m | £2.0m |
| May | £40.8 | £27.9 | £14.8 to £49.4 | £9.0m | £1.4m | £2.1m |
| Jun | £45.5 | £43.4 | £19.4 to £65.2 | £7.5m | £4.0m | £2.0m |
| Jul | £38.4 | £40.4 | £15.2 to £57.5 | £6.0m | £3.7m | £2.1m |
| Aug | £38.5 | £40.6 | £15.6 to £57.5 | £5.9m | £2.8m | £1.9m |
The last row is 28 days annualised. A month closes on the first refresh after it ends, and the figure for the month in progress moves until then.
What this is, and what it is not
Clean Horizon publishes a monthly Storage Index for fourteen European countries: the annualised gross revenue a reference battery would have earned, simulated against that month's prices at one and a half cycles a day. Modo Energy publishes a Great Britain benchmark that includes an estimate of wholesale trading. This page is neither. Every pound on it was paid to a real, named battery and appears in a published file: accepted balancing offers, auction awards at their clearing price, capacity agreements at the price they cleared. That makes it smaller than a modelled total, and it makes it something a modelled total cannot be, which is checkable. In the units the European indices use, £49.4 per kilowatt a year is £49,400 per megawatt a year.
The gap between this floor and any modelled total is the wholesale line, the one revenue stream in Great Britain that no public file records. We publish an estimate of it separately and never add the two together. The panel is deliberately smaller than the fleet: 3,589 MW of the working fleet's 6,849 MW, because a battery that arrived during the year would move the line for reasons that have nothing to do with the market.
Refreshed with the rest of the site on Tuesdays and Fridays. The series as a file, with the twelve monthly figures for every battery in the panel, is here for key holders; the chart and every number on this page are open. How it is worked out