GB battery revenue index: how it is built
The Delivery Year GB battery revenue index is revenue per MW of export capacity earned by 88 site-level GB batteries (5,815 MW), annualised and before costs. For the 30 days to 10 October 2026 it reads £72,972/MW/yr; September 2026 reads £70,115/MW/yr. It is rebuilt from Elexon settlement data and NESO auction and Capacity Market records, and is not a forecast.
Data as of 10 October 2026. Built only from public data and our published method. Information only, not advice.
What the index measures
Revenue earned over the latest 30 settlement days, divided by export capacity (MW) and multiplied by 365/30: an annualised run-rate before costs, in £ per MW per year. The sample is site-level GB battery Balancing Mechanism units, transmission- and distribution-connected, metered in both 30-day windows and active. Supplier and secondary units that combine sites, aggregator units and auction-only units are left out. MW is the owner's rating where published and not above metered capacity, otherwise Elexon's generation capacity.
Across the batteries in the latest window, the 10th, 50th and 90th percentiles are £4,714, £76,623 and £106,358 per MW per year. Of the 30-day headline, £15,763 is measured and £57,209 modelled.
Revenue streams and sources
| Stream | September 2026 (£/MW/yr) | Basis | Source |
|---|---|---|---|
| Wholesale trading | £60,724 | Modelled (our estimate) | Elexon metered output minus accepted Balancing Mechanism volume, valued at the half-hourly market index price |
| Response and reserve | £15,076 | Measured | NESO EAC auction results by unit, dated by EFA day |
| Balancing Mechanism | −£11,818 | Measured | Elexon indicative bid and offer cashflows, checked against volumes and prices |
| Capacity Market | £6,133 | Measured | Contracted de-rated MW times clearing price; T-4 agreements CPI-indexed |
| Total | £70,115 |
Wholesale is modelled, not realised trading revenue. Trading that sells above or buys below the half-hourly average (intraday, auctions, Balancing Mechanism timing) is not observable in public data, so batteries that trade actively can earn more than this estimate. Imbalance sits inside wholesale at the market index price, not the system price.
Sub-indices
Same method, sample and window as the headline index, on sub-fleets. Duration is owner-published or the Capacity Market duration class; 13 batteries (785 MW) have no published duration and sit only in the headline and region/connection indices. Scotland means the battery's GSP group or postcode area is in Scotland, or its register entry is in the SP Transmission or SSEN Transmission area (NESO TEC) or in Scotland (DESNZ REPD); 18 batteries (1,851 MW) could not be placed and sit outside both region indices. Transmission means a directly connected BM unit; distribution means an embedded (DNO-connected) BM unit. A sub-index is published only when at least 3 batteries qualify.
| Sub-index | 30-day run-rate (£/MW/yr) | September 2026 (£/MW/yr) | Batteries | MW |
|---|---|---|---|---|
| About 1 hour (under 1.5 h) | £73,613 | £74,896 | 24 | 1,231 |
| About 2 hours (1.5 h to under 3.5 h) | £80,104 | £75,871 | 50 | 3,748 |
| 4 hours and longer (3.5 h or more) | Not published | Not published | 1 | 50 |
| Scotland | £74,148 | £71,155 | 15 | 884 |
| England and Wales | £66,313 | £63,867 | 55 | 3,080 |
| Transmission-connected | £74,171 | £69,495 | 38 | 3,779 |
| Distribution-connected (embedded) | £70,746 | £71,264 | 50 | 2,036 |
Monthly history
The monthly series runs from February 2019 to September 2026, with 81 published months. 11 months in that span are withheld because a quality check failed; each is listed with its reason. Earlier months are not published: NESO's frequency response tender results, then most battery revenue, are available as data only from January 2019 delivery.
Quality controls
| Control | Check | If it fails |
|---|---|---|
| BM volume check | Periods with Balancing Mechanism cash but no accepted volume: at most 1% | Month withheld with the reason (history gaps) |
| BM price check | Accepted bid-offer pairs priced outside the submitted bid-offer data: at most 1% | Month withheld with the reason |
| Complete months only | At least 28 days in the sample | Month not published |
| Reconciliation | History month against headline month: within 5% | Build fails; nothing is published |
| Restatements | Every change to a published value is logged | Logged in the restatement log and the PDF |
Restatements
Monthly figures are restated when a rebuild moves them by more than 1% and more than £500/MW/yr. Causes: Elexon settlement reconciliation runs (Initial, then R1 to R3 and the final run up to 14 months later), late or corrected NESO auction results, and corrected Capacity Market records. The first published value is kept; each restatement is listed here with both values and the date. Nothing is restated silently.
| Month | First published | Was (£/MW/yr) | Now (£/MW/yr) | Change | Logged |
|---|---|---|---|---|---|
| September 2026 | 17 October 2026 | £56,177 | £67,935 | +20.9% | 17 October 2026 |
| September 2026 | 17 October 2026 | £67,935 | £69,794 | +2.7% | 17 October 2026 |
| September 2026 | 17 October 2026 | £56,177 | £70,115 | +24.8% | 18 October 2026 |
| September 2026 | 17 October 2026 | £69,794 | £70,115 | +0.5% | 18 October 2026 |
Governance
Delivery Year assesses the index against the 19 IOSCO Principles for Financial Benchmarks (July 2013). On the edition of 19 October 2026: 15 met, 1 partly met, 2 not yet met and 1 not applicable. The assessment has not been independently reviewed. The index is an information product and is not offered for use in financial contracts or to measure the performance of investment funds; Delivery Year is not authorised or registered by the Financial Conduct Authority as a benchmark administrator.
Limits
- Coverage: 18 of 88 batteries (1,210 MW) have no response or reserve results published against their own unit this month. NESO publishes aggregator-unit results without naming the batteries inside them, so response sold through an aggregator is not counted.
- 86% of the index MW is matched to a Capacity Market agreement by site name, unit id or applicant; the rest shows no Capacity Market income.
- Indices that include aggregator units read higher on response and reserve than this site-level sample.
- A run-rate over one window, annualised; not a forecast.
The full methodology document and the governance statement are in the Batteries section of the app.
Questions
What is the GB battery revenue index?
A measure of revenue per MW of export capacity earned by site-level GB grid batteries, annualised and before costs. For the 30 days to 10 October 2026 it reads £72,972/MW/yr across 88 batteries (5,815 MW).
How is the battery revenue index calculated?
Revenue over the latest 30 settlement days, divided by export MW, multiplied by 365/30. Balancing, response and reserve, and Capacity Market income are measured from Elexon and NESO data; wholesale is modelled from metered output at the half-hourly market index price.
Which revenue streams does the index include?
Wholesale trading (modelled), response and reserve, the Balancing Mechanism and the Capacity Market. In September 2026: wholesale £60,724, response and reserve £15,076, balancing −£11,818 and Capacity Market £6,133, a total of £70,115/MW/yr.
Why can battery revenue indices differ?
Sample and method differ. This index uses site-level metered units only, leaves out aggregator and auction-only units, counts response only where NESO publishes results against the battery's own unit, and models wholesale at the half-hourly market index price rather than realised trades.
Are published index values ever changed?
Yes, through a logged restatement when a rebuild moves a month by more than 1% and more than £500/MW/yr, mostly because Elexon settlement runs are reconciled for up to 14 months. The first published value is kept and every change is listed with both values and the date.
Can the index be used in contracts?
No. It is an information product, not offered for use in financial contracts or to measure fund performance, and Delivery Year is not an FCA-authorised benchmark administrator.
Sources
- Elexon: BMRS and Insights API (settlement, balancing and market index data) · BMRS data licence
- NESO Data Portal: response and reserve auction results by unit (EAC), Capacity Market register and auction results · NESO Open Data Licence
- ONS: CPI index (D7BT), for Capacity Market indexation · Open Government Licence v3.0
- IOSCO: Principles for Financial Benchmarks (July 2013)
Figures are a snapshot of the latest published data and are rebuilt with every data refresh. Check primary sources before relying on any figure. Methodology & data use · Plans