The headline number is measured revenue per megawatt of active battery capacity, computed from public settlement and auction records over the trailing four quarters. Some figures carry "≥" because the wholesale line is a deliberate floor: the marking convention undercounts trading revenue, and the caveats are measured on page 5. The index is not traded revenue, not a forecast, and not an appraisal of any individual project. Every classification and convention is listed on page 4, and every known limitation is measured on page 5. Methodology changes are pre-announced with dates and are never applied retroactively.
This report is the settled record. Its living companions, updated between quarters: the provisional monthly series · the per-asset lookup · the GB fleet & pipeline map.
Per-quarter annualised revenue per active MW. Frequency response shrinks as the fleet grows and FR prices saturate; the Balancing Mechanism absorbs the MW. Capacity Market is an annual stream (dashed window-level line) — it has no quarterly settlement basis. The former combined "Frequency response" line is shown split into response (DC/DM/DR) and reserve (QR/BR/SR) — a presentation change registered 2026-07-23; the two segments stack to exactly the published total.
| Frequency response (DC/DM/DR) | £14.4k | 45.6% | |
| Balancing Mechanism | £12.2k | 38.8% | |
| Reserve (QR/BR/SR) | £3.0k | 9.6% | |
| Capacity Market | £2.2k | — | |
| Wholesale (floor)ᶠ | £1.9k | 6.0% | |
| Total measured | ≥ £33.7kᶠ | 100% |
Across the metered GB battery fleet (168 BMUs / 6.7 GW registered). Initial settlement; figures revise.
The wholesale figure is the metered-at-MID floor: every metered MWh marked at the Elexon market index. The convention charges the fleet's round-trip losses and its BM/FR-instructed throughput to this line — in 2026Q2 the fleet charged 1,029 GWh against 862 GWh discharged — so for genuinely trading units true arbitrage revenue is HIGHER than this line. The "≥" direction holds at fleet level only (limitations, page 5): MID also CREDITS delivered response energy that settlement prices at zero, and non-battery behaviour inflates class-level floors — class floors carry no "≥" guarantee (corrections record, page 5). The floor is published beside its re-measured companions — BOA-netted, TLM-adjusted (page-1 table) and ABSVD-netted (page 4). We publish the measured floor rather than a modelled gross-up — totals carrying it are marked ᶠ.
Market-comparable context (registered 2026-07-23; not a settlement measurement): the 2h-class traded-spread companion — mean daily top-2h−bottom-2h MID spread £64/MWh × the measured 24.3% capture — reads ≈ £11.4k/MW·yr beside this floor. Full table on page 6.
In plain terms: the wholesale number deliberately undercounts what trading units earn; that undercount promise holds for the fleet total, not for each class, and every measured exception is on page 5.
| Series (£/MW·yr) | Fleet | 1h | 2h | 4h | Window £ |
|---|---|---|---|---|---|
| Wholesale floor (gross, published)ᶠ | £1.9k | £1.5k | £5.3k | £5.9k | £11.4M |
| BOA-netted | £5.5k | £-0.4k | £23.5k | £17.3k | £33.0M |
| BOA-netted + TLM | £4.5k | £-1.0k | £22.1k | £16.3k | £27.2M |
Two of the pre-announced 2026Q3 basis changes (page 5) are measured here as companions; the published floor above is unchanged until the window advance, and nothing is restated. BOA-netted removes accepted Balancing Mechanism energy from metered volume before MID-marking, so the wholesale and BM lines stop double-marking the same MWh: in 2026Q2, accepted offers were 41% of fleet discharge and accepted bids 55% of fleet charge, and netting them moves that quarter's floor by +£20.1M (the gross line UNDERSTATES that quarter); across the window the netted floor sits +£21.7M from gross. + TLM then credits metered energy the way settlement does — Transmission Loss Multipliers per settlement period, delivering on discharge and offtaking on charge, each unit's zonal loss factor entering as a class-weighted mean. Applied to a net floor whose gross legs dwarf it, the measured TLM effect is −£5.8M (−51% of the trailing floor); the composed series ends +£15.9M from gross. Where a companion line runs negative, that is the measurement, printed. Sources: Elexon BOAV settlement acceptance volumes and SAA settlement-run TLM data (the run used per day, per-quarter series and gross-line reconciliation ship in the evidence JSON and the data pack).
Each dot is one BMU's trailing-year measured revenue per MW under the index conventions (wholesale floorᶠ + EBOCF net BM + EAC FR; registry-MW denominator). Bars mark P25/median/P75; the median is copper. Units active in all four quarters only (survivor cohort: 122 of 168 registry BMUs; 9 excluded on the disclosed capacity-plausibility screens — see page 4); 7 units have negative measured totals (real, convention-driven: BM-instructed charging pays out in the wholesale leg). Spread partly reflects strategy and location, not only operator skill. Classes with too few screened units for stable percentiles (4h) are not shown. Per-unit totals are NOT individually "≥" floors: with no BOA netting, offer-heavy units can be overstated and bid-/response-heavy units understated — the floor direction holds at fleet level only. This strip orders 2h ahead of 1h on per-unit medians while the class table below orders 1h ahead on MW-weighted totals — its premium sits in the FR leg: the 2h class carries a heavy left tail (curtailment-zone units, some negative) that drags its MW-weighted mean below its median. Both are correct; they answer different questions.
| Class | MW | BM | Resp | Rsv | WSᶠ | CM | Total | cyc/day | spread |
|---|---|---|---|---|---|---|---|---|---|
| 1h | 1,344 | £8.9k | £20.1k | £0.7k | £1.5kᶠ | £3.0k | ≥ £34.2k | 0.84 | 26.5% |
| 2h | 1,773 | £9.9k | £7.4k | £6.0k | £5.3kᶠ | £4.5k | ≥ £33.1k | 0.96 | 24.3% |
| 4h | 313 | £1.5k | £1.6k | £1.2k | £5.9kᶠ | —† | ≥ £10.2k | 0.36 | 25.4% |
Resp / Rsv split the former FR column into Frequency response (DC/DM/DR) and Reserve (QR/BR/SR) — a presentation change registered 2026-07-23; the pair sums to the published FR figure exactly. † CM per-MW/yr withheld where a class was active well short of the full window — annualising full-window CM revenue on a partial-window MW base would overstate it (the £ amount is in the data pack; page 6 carries the entrant-aligned companion that CAN state it consistently). No 8h units exist in the GB fleet yet. The 4h class — a single site — measures as net BM earners this window (£1.5k/MW·yr net BM); the sign has flipped between published windows — a quarter-mix effect, not a stable class property.
£/MW·yr within the 2h class only; the FR side is shown split — response (DC/DM/DR) vs reserve (QR/BR/SR), summing to the published FR figure. 2026Q2 2h BM was NET NEGATIVE (£-2.5k/MW·yr) — drawn below the axis, never clipped to zero.
| Strategy | units | MW | MW share | FR | BM | WSᶠ | Total |
|---|---|---|---|---|---|---|---|
| FR-annuity | 70 | 2,795 | 43.7% | £29.5k | £3.0k | £-0.1kᶠ | £32.5k |
| Mixed | 35 | 1,440 | 22.5% | £13.9k | £20.2k | £4.9kᶠ | £39.0k |
| Trader | 46 | 2,161 | 33.8% | £4.4k | £18.3k | £3.8kᶠ | £26.5k |
Classification registered 2026-07-24, bands frozen: per behaviour-gated unit over the trailing window, FR share = frequency-response £ over (FR £ + BM £ + wholesale-floorᶠ £ clamped at zero); FR-annuity at share ≥ 0.60, Trader at share ≤ 0.25, Mixed otherwise. Informational, never graded; the bands change by a new registration only. Measured this window: the 70 FR-annuity units (43.7% of gated MW) measure a £-0.1kᶠ/MW·yr wholesale floor beside £29.5k/MW·yr of frequency response. The 46 Trader units measure £18.3k/MW·yr in the Balancing Mechanism and £3.8kᶠ/MW·yr on the wholesale floor, with £4.4k/MW·yr of frequency response. The 35 Mixed units measure £13.9k/MW·yr FR, £20.2k/MW·yr BM and £4.9kᶠ/MW·yr wholesale floor — £39.0k/MW·yr combined. The full per-asset dataset behind this panel (151 gated units: strategy class, stream split, within-class percentile, cycling, screens; gate failures in an exclusions disclosure) is published beside the index. In plain terms: 44% of gated battery capacity is run mainly for frequency-response income, 34% mainly trades energy through the Balancing Mechanism and wholesale, and the remaining 22% does both.
| Zone | n | MW | net BM /MW·yr | vs GB | offer leg /MW·yr | |
|---|---|---|---|---|---|---|
| Z2 | 4 | 209 | £-56.4k | -4.62× | £6.0k | |
| Z3 | 3 | 130 | £-17.0k | -1.392× | £3.8k | |
| Z4 | 19 | 730 | £-5.5k | -0.449× | £10.8k | |
| Z5 | 1 | 49 | £1.4k | 0.119× | £1.8k | |
| Z6 | 2 | 68 | £7.5k | 0.611× | £27.7k | |
| Z7 | 15 | 375 | £23.0k | 1.881× | £34.6k | |
| Z8 | 15 | 752 | £26.9k | 2.2× | £38.7k | |
| Z9 | 8 | 275 | £11.7k | 0.958× | £25.8k | |
| Z10 | 9 | 326 | £29.3k | 2.4× | £43.0k | |
| Z11 | 10 | 260 | £14.7k | 1.206× | £21.6k | |
| Z12 | 5 | 167 | £18.3k | 1.496× | £28.0k | |
| Z13 | 25 | 1,222 | £23.1k | 1.893× | £37.4k | |
| Z14 | 15 | 590 | £15.4k | 1.26× | £20.9k |
Net BM = bid + offer EBOCF cashflows: curtailment-absorbing zones (Scottish boundary) are net NEGATIVE because BM-instructed cheap charging is paid-for energy whose value lands in the wholesale leg, not a loss; the OFFER leg (discharge instructions only) is shown alongside. GB mean net BM £12.2k/MW·yr. Postcode area → zone is an approximate hand mapping. Greyed rows have n<3 — treat as indicative. 29 units (887 MW·yr) have no mappable zone and sit in the GB mean only. The best-to-worst spread is £85.7k/MW·yr — siting moves BM revenue more than duration does.
Discharge- vs charge-weighted MID price per quarter (£/MWh, floor-convention legs) with the 2h spread-capture ratio beneath. Mean MID £72 → £74 → £91 → £95; negative-price settlement periods 192 / 30 / 43 / 144 per quarter.
| Product | 2025Q3 | 2025Q4 | 2026Q1 | 2026Q2 | |
|---|---|---|---|---|---|
| DCH | 2.18 | 2.04 | 1.02 | 1.96 | ↓ |
| DCL | 3.61 | 3.14 | 2.35 | 2.70 | ↓ |
| DRH | -2.37 | -2.94 | -7.39 | -8.71 | ↓ |
| DRL | 13.25 | 14.88 | 16.20 | 17.22 | ↑ |
Revenue-weighted mean EAC clearing price across cleared blocks, all battery units. Co-optimised auctions clear negative prices on individual product legs — real, netted as cleared. The FR revenue decline is price-driven, not volume-driven: cleared volume moved +7% across the window while the revenue-weighted clearing price moved -22% (all-battery FR spend -16%).
Bars are ACTIVE metered MW (BMUs with settlement volume in the quarter); the dashed line is the full registry. In 2026Q2, 15 registered-but-inactive BMUs carried £83.6k BM + £1702.6k FR that the index EXCLUDES for denominator consistency. Battery EAC revenue outside the BMU-metered perimeter entirely: £1.71m in 2026Q2 (£31.3k at alias units of registry sites + £1.68m at auction units we cannot map to any BMU), £19.2m over the window = 14.7% of all-battery EAC money (printed in full since 2026-07-23 — corrections record, page 5). It sits outside numerator and denominator alike, so no per-MW figure moves. Forward P50s for your own site under fleet build-out scenarios: the CECadence app at cadence.compoundingenergy.com.
Fleet-level figures in this report are reproducible from public primary data. No third-party benchmark licence. The index is measured from Elexon settlement and NESO auction records for the 168-BMU GB battery registry; conventions and exclusions are quantified where measured, and page 5 quantifies the known measurement limits — including those that reduce the headline. Two derived items (the per-unit screen threshold and the postcode→zone lookup) are available under licence.
| Stream | Primary source | The caveat that matters |
|---|---|---|
| Wholesale (floor)ᶠ | Elexon B1610 per-BMU metered volumes × Elexon MID half-hourly market index | A metered-at-MID floor on arbitrage revenue — losses and BM/FR throughput are charged to this line; not traded positions. |
| Balancing Mechanism | Elexon indicative settlement cashflows (EBOCF), bid + offer netted per BMU | Initial settlement, before reconciliation runs; figures revise. |
| Frequency response / reserve | NESO EAC auction results by unit: clearing price × executed MW × block hours | EFA-day windows (~1h edge mismatch vs settlement days, immaterial at quarter scale); negative product legs netted as cleared; published as split rows — Frequency response (DC/DM/DR) vs Reserve (QR/BR/SR) — since 2026-07-23 (totals unchanged). |
| Capacity Market | NESO CM register: awarded de-rated obligations × acquiring auction clearing prices | Initial-auction basis; secondary trading and penalties not netted; delivery years overlap-weighted into the window. |
| Per-unit distribution | Derived at report build from the same pinned per-BMU caches | Survivor cohort (active all four quarters); capacity_flag units (7) and throughput-implausible units (2) excluded and counted here; the screen definition and threshold ship in the licensed data pack. |
| Inactive registry BMUs (2026Q2) | 15 units | £83.6k BM + £1702.6k FR kept out of the numerators — the denominator only counts metered MW. |
| Non-BM alias FR units (2026Q2) | 17 units | £31.3k FR earned outside the BMU-metered perimeter. |
| Terminated CM agreements | 128 MW | Excluded from CM revenue. |
| CM obligations with no postcode-bearing component | 1,295 MW | Cannot be attached to a site — skipped, not guessed. |
Per-MW figures are active-MW-day weighted: numerators and denominators cover exactly the BMUs with metered volume in each quarter — except CM, which accrues over the full window for any site active in any quarter (mismatch quantified on page 5). The wholesale line is a metered-at-MID floorᶠ, reported separately from BM cashflows (no BOA netting; the overlap is first-order, quantified on page 5 and measured as the page-1 BOA-netted companion). Cycles divide metered discharge by MW × CM-register duration hours. One registry, composed as of the build date; entry and exit are handled by per-quarter active scoping (part-quarter entrants count at full-quarter MW-days — page 5). Initial settlement for the newest quarter; older quarters are pinned at their fetch vintage (restatement policy — page 5); figures revise. Public cross-check: the measured 2h cycles (1.07/day in 2026Q2) sit BELOW the public 1.2–1.5 band. We publish the measurement, not the band. Full conventions ship in the evidence JSON (/api/index) and the data pack.
Duration-class provenance. Classes come from the CM register's duration bands ("Generating Technology Class"): each site takes the band carrying the most registered MW across its capacity-market components. Units with no CM band stay in the fleet totals but sit outside the class tables — 70 active units (2,993 MW, ~45% of active fleet MW) in this window. The register is a registration, not a measurement: a metered-implied duration audit (the p99.5 contiguous discharge run per unit over the window, 2025Q3–2026Q2) found 9 of 40 "1h"-banded units (377 MW, 25% of the class) sustaining ≥1.5h, and the published "4h" class is a single site behaving as 2h — a conservatively registered or since-augmented asset's revenue sits in its registered band's row, blending adjacent class figures. From 2026Q3 the primary classification moves to metered-implied duration, dual-published against this CM-band cut for continuity, which also brings the un-banded fleet into the class split. Like-for-like, reclassifying the banded universe leaves 1h and 2h within 2% of each other — the class similarity is carried by the EAC frequency-response leg, not by banding. In plain terms: a battery's duration class comes from its registration paperwork, not its measured behaviour, and the paperwork disagrees with behaviour often enough to blur the class rows — the disagreement is measured here, with the dated fix.
ABSVD treatment. Measured in both bases. Energy delivered by primary BM Units under NESO frequency-response contracts is removed from imbalance settlement via ABSVD (deemed volumes; NESO's C16 methodology), so that energy is neither bought nor sold at market prices, while the wholesale floorᶠ marks ALL B1610 metered volume at MID — penalising response-heavy units. Per-BMU Applicable Balancing Services Volumes are freely published on Elexon's Insights API (dataset QAS, per settlement period, history to 2022; access probe dated 2026-07-23 — corrections record, page 5). The ABSVD-netted companion ((QM − QAS) × MID) is published beside the floor: fleet £1.9k → £3.8k; 1h £1.5k → £-1.3k; 2h £5.3k → £14.2k; 4h £5.9k → £22.8k/MW·yr (un-netted → netted). The audit's expectation is NOT confirmed as measured: netting lowers the FR-heavy subset (88 units, 3.4 GW — the audit's ≈−£1,666/MW·yr cohort) from £-1.7k to £-7.4k/MW·yr (50 → 38 units with a negative floor), and does not raise the short-duration class floors. The mechanism, measured: that cohort's ABSVD is net DELIVERED response which the un-netted floor had been crediting at MID; charge-side response dominates the longer classes, where netting hands the credit back. The un-netted floorᶠ remains this window's published basis; netting becomes the dual-published basis at the 2026Q3 re-basing (pre-registered). FR revenue itself is EAC contracted results, unreachable by settlement adjustments; BM is accepted-BOA cashflows, which ABSVD does not adjust. Secondary and non-BM units receive no frequency-response ABSVD and largely sit outside the B1610 universe — a disclosed composition limit (BSC Issue 114 / P502 are live on exactly this). In plain terms: the floor convention prices energy that settlement never traded, which penalises response-heavy units; the corrected companion figure is printed beside the floor above.
Availability basis (per-MW denominators). The active-MW-day denominator is quarter-clean and intra-quarter dirty: a unit counts only in quarters with any metered volume, but outage days within an active quarter remain in the denominator — per-MW figures are net of intra-quarter downtime. The survivor cohort on page 2 (122 of 168 registry BMUs) is the fixed-composition year-on-year cut. In plain terms: a battery that sat idle for days inside an active quarter still counts at full size in the denominator, so per-MW figures absorb that downtime.
MID — Elexon's half-hourly Market Index Data price; the report values every metered megawatt-hour at it.
EBOCF — Elexon's estimated bid and offer cashflows: the money paid or repaid for accepted Balancing Mechanism actions.
EAC — NESO's Enduring Auction Capability, the frequency-response and reserve auction; revenue is cleared price × contracted MW × block hours.
BOA — a bid-offer acceptance: a charging or discharging instruction the system operator accepted in the Balancing Mechanism.
ABSVD — deemed energy volumes that settlement removes for delivered frequency response, so that energy is never traded at market prices.
TLM — Transmission Loss Multipliers: per-settlement-period factors that adjust metered energy for grid losses; not yet applied to this index.
Initial settlement — Elexon's first settlement run for a period; later reconciliation runs revise the figures.
Active-MW-day weighting — per-MW figures count each battery by its capacity × days, in quarters where it metered volume.
ᶠ marker — flags any figure that contains the wholesale floor line, so the marked figure is itself a floor.
CM derating — Capacity Market revenue is de-rated obligation MW × clearing price; de-rating scales capacity down from nameplate.
One entry per limitation: what · measured magnitude · consequence for the reader · status. Magnitudes are from the adversarial audit dated 2026-07-23, run against the pinned 2025Q3–2026Q2 caches and independently verified; they are stated two-sided where the exposure runs both ways. No entry changes this window's published basis — basis changes are pre-announced in the dated box below, number-changing corrections are collected in the dated record, and none applies retroactively.
The battery-definition gate. Registry entry trusts the EAC "Batteries" tag; no behavioural screen is applied. Five units with trailing discharge/charge above 1.05 — 2.6% of active MW — supply 51% of the fleet wholesale floor. Floor under alternative gates: £1,884 published · excluding the five £949/MW·yr · a two-sided 0.5–1.02 behavioural band £2,460 · excluding only the charge-only low tail £3,362. Excluding two aggregator portfolio units cuts the 2h-class floor −29%. Consequence: the wholesale line is not robust to the gate, in either direction; the composite ≥ total moves ~±2%. Status: behavioural gate pre-announced for 2026Q3 (box below). In plain terms: some units we counted as batteries are not batteries, and they flattered this line; the size of the flattery is measured above.
Registry membership is conditioned on EAC participation. A unit enters only with a BM registration plus at least one EAC battery clearing since April 2025; batteries trading wholesale/BM only are invisible (≈0 effect on this window's EAC-participant perimeter; the never-EAC cohort is not quantifiable from our data). One aggregator-to-primary migration double-counts ~21 MW in one quarter's denominator (−0.35% that quarter, under 0.1% trailing). 28 portfolio BMUs (825 MW, 22% of classed registry MW) take their duration class from a single site's postcode; portfolio units are 27% of active 1h-class MW and 16% of 2h. Consequence: the perimeter understates the never-EAC fleet and class rows carry portfolio-attribution risk. Status: membership widening pre-announced for 2026Q3 (box below). In plain terms: a battery that never entered the auctions is invisible to this index, so the fleet measured here is a subset of the real fleet, of unmeasured size.
Transmission Loss Multipliers are not applied. The net floor is the difference of gross legs 47× its size, so small multipliers lever hard: a 0.5% directional TLM cuts the trailing floor 23% (and the weakest quarter −84%); at 1.0% that quarter flips negative. Consequence: TLM runs AGAINST the ≥ mark on this leg; headline exposure −1.3% to −2.6%. Status: applied at the 2026Q3 re-basing. Measured as a page-1 companion this window: the applied TLMs move the trailing floor by −£5.8M (−51%). In plain terms: settlement scales metered energy for grid losses and this index does not yet; the scaling works against the wholesale line's floor promise, at the size measured above.
The MID mark is single-venue prompt VWAP. The index price is the APX (EPEX UK) prompt volume-weighted price alone — the N2EX series carries ≤0.005% of MID volume — not the day-ahead-auction basis battery wholesale trading is optimised against. Consequence: at ~24:1 gross-to-net leverage, a re-mark could move the wholesale line by tens of percent either way (headline ~1–3%). Status: convention stands; the traded-spread companion (pages 1 and 6) is the market-comparable context. In plain terms: the price used to value metered energy comes from one trading venue, and it is not the price most batteries optimise against; a different price choice could move the wholesale line by tens of percent.
The BM-energy/wholesale overlap is first-order. In 2026Q2, accepted-BOA offer energy was 41% of fleet discharge and BOA bid energy 46% of fleet charge; marked at MID that is +£31.9M (offer-side double-count) against −£43.2M (bid-side double-charge), net −£11.4M. Consequence: the published total UNDERSTATES that quarter; no BOA netting remains the stated basis, with the overlap shipped quantified. Status: BOA netting joins the dual-published basis at 2026Q3. Now measured across all four quarters as the page-1 BOA-netted companion: +£21.7M on the trailing floor. In plain terms: the same energy can be counted once in the balancing line and once in the wholesale line; the net effect understates the latest quarter's total, at the size measured above.
The FR stream includes reserve, on a contracted basis — now shown split. 17.4% of the trailing stream (£18.3m of £105.1m) is reserve revenue (Quick/Balancing/Static Reserve); the stream is CONTRACTED auction revenue — availability and performance scaling are not netted (plausible gap under 1% of the headline) — and £2.16m/yr of alias FR is earned at sites whose MW IS in the denominator (per-MW FR biased low ~2%). Consequence: the ~21%-lower response-only comparison reads directly off the rows — "Frequency response (DC/DM/DR)" vs "Reserve (QR/BR/SR)". Status: split applied throughout, registered 2026-07-23 (totals unchanged). In plain terms: the frequency-response line has always included reserve contracts as well, and it counts what the auctions awarded, not what was delivered; the two families now print as separate rows.
Battery EAC revenue outside the BMU perimeter. £19.2m over the window (14.7% of all-battery EAC money) is earned at alias and unmappable auction units; the full split is on page 3. Consequence: no published per-MW figure moves — the revenue sits outside numerator and denominator alike. Status: printed in full since 2026-07-23 (corrections record below). In plain terms: real battery auction money is earned at units this index cannot tie to a metered site; it is excluded from both sides of the division, so no per-MW figure moves.
CM is understated and its out-of-registry universe is mostly non-battery. Clearing prices are applied nominal, not CPI-indexed to delivery year: a systematic ~8–9% CM understatement (fleet £2,187 → ~£2,362–2,406/MW·yr). The £76.5M out-of-registry drop over the window is ~63% pumped hydro; of the ~£40.4M battery CM universe the index captures ~33%, ~£6.7M/yr is evidence-backed join failure whose repair would raise fleet CM ~+51%, and 56% of active MW carries zero CM in the numerator. Consequence: CM per-MW reads low and cross-class CM comparisons inherit the join gaps. Status: CPI indexing applies at 2026Q3, measured now as the page-6 companion; the attachment caveat is corrected in the dated record below. In plain terms: the Capacity Market line reads low — prices are not inflation-adjusted and some contracts fail to match to sites — and each measured shortfall is stated above.
Weighting and vintage. Part-quarter entrants count at full-quarter MW-days (entrant MW was 13.4/9.0/4.6/4.9% of the four quarterly denominators; the heaviest quarter's per-MW figures are understated by up to ~5.7%, the trailing year plausibly ~2%). CM accrues over the full window for mid-window entrant sites while the denominator counts active quarters only — fleet CM +4.8% overstated, the 1h class +15.1%. Capacity and duration class are as-of-build-date, applied retroactively (plausibly under 1%). Quarters are pinned once at settlement ages from three weeks to eight-plus months: measured revision drift is zero on BM cashflows and leaves per-quarter wholesale lines soft by up to ±19% (≈0.1% of the headline). Consequence: entrant-heavy quarters read conservative; the newest quarter is the softest. Status: proration and realigned CM accrual apply at 2026Q3, measured now as the page-6 companion; pinned initial-settlement quarters are never silently restated — an RF-basis restatement is published annually as a separate, dual-published vintage. In plain terms: new units count as if present for their whole first quarter, and each quarter keeps its first-published settlement numbers; both effects are measured above, and they do not all lean the same way.
The headline above is a public-data floor basis. Each row below is a measured quantity from our own open inputs, applied in the fixed order shown on the published CM-banded cohort (2025Q3-2026Q2); legs we cannot measure from open data are named and left in the residual — none is a plug, and no leg is derived from a benchmark figure. Benchmark: Modo Energy's ME BESS GB, the FCA-regulated benchmark; its conventions are taken from its public methodology page (version 3.1, last updated 2026-05-18, read 2026-09-15). Consequence: the bridged totals are the closest like-for-like reading of this record under the benchmark's conventions that open data supports; what remains is named, not estimated. Status: the benchmark column is off; with it off this page prints no benchmark figure and no ratio.
| Leg (in waterfall order) | What differs | Fleet £/MW·yr | 2h £/MW·yr | Basis |
|---|---|---|---|---|
| Published headline, ex-CM | the 2025Q3-2026Q2 record above (wholesale floor + BM + response/reserve) | 31,494 | 28,605 | published |
| 0. Reserve availability shown as its own stream | reserve availability shown as its own stream (total unchanged) | 0 | 0 | measured |
| 1. Capacity Market inside the total | Capacity Market inside the total (incl-CM only) | +2,187 | +4,479 | measured |
| 2. BOA energy netted out of the metered wholesale volume | BOA energy netted out of the metered wholesale volume | +3,588 | +18,210 | measured |
| 3. ABSVD (delivered response/reserve energy) netted out | delivered response/reserve energy (ABSVD) netted out | +1,895 | +8,843 | measured |
| 4. ≥6 MW asset screen | units under 6 MW screened out | +1,311 | 0 | measured |
| 5. Entrant-aligned (prorated) MW-day divisor | MW-days from each unit's entrant quarter; CM accrual realigned | -642 | 0 | measured |
| 6. CPI indexation of Capacity Market clearing prices | CM clearing prices CPI-indexed (incl-CM only) | +198 | +410 | measured |
| Bridged total, ex-CM | published + the measured legs that apply to the ex-CM total | 37,646 | 55,658 | 7 measured · 0 not computed |
| Bridged total, incl-CM | published ex-CM + every measured leg incl. the CM line | 39,916 | 60,502 | measured |
Legs 1 and 6 enter the incl-CM total only; the ≥6 MW screen and the proration leg also re-scale the CM line, and those CM-side effects sit inside the incl-CM total (carried per leg in the artifact). Reserve split as published: fleet response £14,374 / reserve £3,029 per MW·yr. Balancing Reserve is absent from this record for 2025Q3 (excludes Balancing Reserve — NESO EAC-BR results dataset not fetched).
| Companion | Why it is not a leg | Fleet £/MW·yr | 2h £/MW·yr |
|---|---|---|---|
| Transmission Loss Multiplier on metered volume (§17.4) | a CE settlement-basis companion — the benchmark's public wholesale definition is PN volume at day-ahead prices and does not mention a loss multiplier, so it is not a benchmark-direction leg | -960 | -1,399 |
| Behavioural battery gate (§17.1) | a CE proxy screen, not the benchmark's shared-meter rule; 17 units / 589 MW gated out | +502 | — |
| Registry membership widened beyond EAC participants (§17.9) | 8 candidate units with metered volume (367 MW); 1 gated in (31 MW) | — | — |
| Metered-implied duration classes (§17.2) | the 2h class re-cut by metered-implied duration through CE's own edges (not the 2.5 h edge): 3,351 MW, total incl-CM +34,707/MW·yr — shown beside, never mixed | — | — |
2H cut, published beside the 2h class (never mixed). The CM-declared 1.5 ≤ h < 2.5 cohort (43 units, 1,752 MW active-MW-day weighted) on the same waterfall: ex-CM £27,635 → bridged ex-CM £56,105, incl-CM £60,928/MW·yr. Duration bases side by side: published 2h class = 1.5–<3.0 h (CM register); this cut = 1.5–<2.5 h (CM register); metered-implied = the companion row above; the benchmark's = rated energy/power per its methodology page (§4.2.2), a field CE's open inputs do not carry. No public 2H print exists for this window.
Where our convention understates (measured legs that move the fleet figure up): Capacity Market inside the total; BOA energy netted out of the metered wholesale volume; ABSVD (delivered response/reserve energy) netted out; ≥6 MW asset screen; CPI indexation of Capacity Market clearing prices. Where it overstates (measured legs that move it down): Entrant-aligned (prorated) MW-day divisor.
Named residual components — what remains after the measured legs, with the input each needs; no magnitude is assigned: Wholesale price basis — day-ahead (N2EX/EPEX) and RPD marks vs Elexon MID (needs licensed N2EX/EPEX day-ahead and EPEX RPD price series (not open data)); Contracted-PN volume basis and the imbalance term (needs per-BMU Physical Notifications, system prices and per-period ABSVD (v2 fetches)); Rated power vs registered export limit / max executed MW in the divisor (needs rated power per asset (no open field)); 'No shared meter' screen and the FPN-or-contract daily activity rule (needs a co-location field and per-day FPN submissions); Balancing Reserve availability (separate NESO EAC-BR dataset) (needs the EAC-BR results dataset (v2 back-fill under its own protocol section)); Battery auction revenue outside the BMU perimeter (bracket on the residual row) (needs a unit-to-site mapping for alias and aggregator auction units); Availability/performance scaling and the EFA-day vs settlement-day edge (needs per-unit performance-monitoring outcomes); Settlement-run vintage of the pinned data vs the benchmark's revision ladder (needs docs/evidence/bess_index_restatement.json (first committed at the 2026Q3 advance)); Universe composition (the benchmark's asset list vs the CE registry as-of build date) (needs the benchmark's asset list (not published)); LCCC monthly payment weighting of CM within the window (needs the public LCCC monthly weighting profile applied per delivery year (v2 table)); Capacity Market obligations not attached by the postcode join (coverage bracket on the residual row) (needs a CMU-to-BMU join beyond postcode). Brackets on the residual row of the artifact: battery auction revenue outside the BMU perimeter, and the share of register storage-CMU obligations the postcode join attaches.
History coverage. reserve split measured from 2023Q4 (FR not measured 2022Q1–2023Q3; 2023Q4 partial); BOA netting from 2025Q1; ABSVD netting from 2025Q3; ≥6 MW screen every quarter from 2022Q1; Capacity Market, proration and CPI indexation on the trailing window only. Balancing Reserve: 2024Q2, 2024Q3, 2024Q4, 2025Q1, 2025Q2, 2025Q3 carry 'excludes Balancing Reserve — NESO EAC-BR results dataset not fetched'. Pre-EAC rows carry 'FR not measured' and no benchmark delta.
In plain terms: our headline is built on deliberately conservative conventions; this table shows, one step at a time and from our own data, how far those conventions move the number toward the way the regulated benchmark counts, and names what remains unmeasured. No benchmark figure is printed here.2026-07-23 · out-of-perimeter FR corrected £31.3k → £1.71m (2026Q2; the prior print carried the alias slice only — a 55× understatement) · page-3 figures restated; per-MW figures unaffected
2026-07-23 · per-BMU ABSVD access re-classified: the "S0142 settlement reports via the P114 service only" claim was measured WRONG by a dated access probe (2026-07-23) — Elexon's Insights API publishes dataset QAS freely · ABSVD-netted companion published (page 4)
2026-07-23 · CM attachment caveat corrected — one pumped-storage station is 65% of the prior "1,295 MW cannot be attached" figure · battery-side skip was overstated ~2.8×
2026-07-23 · BM/wholesale overlap re-classified from marginal to first-order and quantified · 2026Q2 net −£11.4M; measured as the page-1 companion
2026-07-24 · the 2h-class floor guidance withdrawn (measured 41% inflated by non-battery units) · class-level floors carry no "≥" guarantee
2026-07-24 · 2026Q2 entrant share corrected: 4.9% counted a post-idle return as an entrant · returns shown separately from entrants (page 6)
2026-09-15 · the hand-typed benchmark-context paragraph (iteration 181; its ratio and two magnitudes were not reproducible from any committed artifact) retired · replaced by the computed bridge section above, sourced only from the reconciliation artifact; no benchmark figure or ratio is printed while the benchmark column is off
2026-09-28 · the metered-implied duration computation corrected to the registered wording — one p99.5 quantile over the window's pooled contiguous-discharge sums, not the per-quarter maximum the July preview used · 9 units / 322 MW change class in the page-7 cut (eight 2h → 1h, one 4h → 2h); the "1h"-band finding on page 4, on the same ungated CM-banded universe, reads 9 of 40 units (377 MW) where the July print read 16 of 40 (606 MW) — the computation changed, not the universe; no published figure moves
No correction applies retroactively to a pinned quarter. The full trail is in the CECadence changelog; everything else in this report states the current convention.
The number-changing corrections, collected in one place: (1) primary duration classification moves to metered-implied duration, dual-published against the CM-band cut; (2) a behavioural battery gate on the registry, with the excluded units and £ published as a disclosed exclusion; (3) CM clearing prices CPI-indexed to delivery year; (4) Transmission Loss Multipliers applied to marked volumes; (5) part-quarter MW-day proration from first metered day, and CM accrual aligned to active quarters; (6) registry membership widened beyond the EAC-participation condition; (7) ABSVD deemed-volume netting — its access condition was RESOLVED early by a dated probe (2026-07-23): per-BMU QAS volumes are freely published on Elexon's Insights API (the S0142/P114 settlement-report route is not needed for volumes), so the netted companion already appears on page 4 of this report and netting joins the dual-published basis at the re-basing; (8) a traded-spread wholesale companion line published alongside the floor. Every change to the graded basis goes through pre-registration before application; none is applied retroactively; all are dual-published for continuity. Measured companions for (3), (5) and (8) now ship on page 6 (registered 2026-07-23) beside the published basis, and the response/reserve split from the same registration is APPLIED throughout this report — presentation and naming only, totals unchanged.
Registered 2026-07-23; every basis change applies at the 2026Q3 window advance only and will be dual-published against the outgoing basis for at least four quarters. Nothing on this page changes a published figure — each companion is measured NOW so the 2025Q3-2026Q2 record carries both readings. The frequency-response/reserve split from the same registration is APPLIED throughout this report (presentation and naming only; every split pair sums to the published total exactly).
| Class | published £ | CPI-indexed £ | uplift | published /MW·yr | indexed /MW·yr |
|---|---|---|---|---|---|
| 1h | £4.05m | £4.58m | +13.0% | £3.0k | £3.4k |
| 2h | £7.94m | £8.68m | +9.3% | £4.5k | £4.9k |
| 4h | £1.22m | £1.22m | +0.0% | —† | —† |
| Fleet | £13.21m | £14.47m | +9.6% | £2.2k | £2.4k |
CM clearing prices indexed from auction-year to delivery-year money per the Capacity Market's own mechanism (Electricity Capacity Regulations 2014 Sch. 1: winter-average (Oct–Apr) CPI ratio; T-4/T-3 prices only — T-1 clearing prices are not CPI-adjusted, which is why the all-T-1 4h class moves +0.0%). ONS series: CPI all items, CDID D7BT, dataset MM23 (2015=100); the Regulations name "CPI" without an ONS series id, so D7BT is the documented choice. Factors this window: 2024-25 T-4 ×1.2110; 2025-26 T-4 ×1.1736; the statutory base period is set per auction — the winter ending in the auction-held year is a disclosed approximation. Measured: measured fleet uplift +9.6% (£2,187 → £2,397/MW·yr) — inside the audited ~+8–9% expectation band (£2,362–2,406/MW·yr): the Rules' mechanism indexes T-4/T-3 prices only, on winter-average CPI, so the all-T-1 4h class stays at +0.0% while the T-4-heavy 1h class runs above the fleet mean. † withheld on the published basis (partial-window class); the entrant-aligned companion below states it consistently.
| Class | MW·days Δ | BM /MW·yr | FR /MW·yr | WSᶠ /MW·yr | CM realigned £ | CM Δ | CM /MW·yr |
|---|---|---|---|---|---|---|---|
| 1h | +3.8% | £8.6k | £20.0k | £1.4kᶠ | £3.64m | -10.3% | £2.6k |
| 2h | +0.0% | £9.9k | £13.4k | £5.3kᶠ | £7.86m | -1.0% | £4.4k |
| 4h | +0.0% | £1.5k | £2.8k | £5.9kᶠ | £1.22m | +0.0% | £5.2k |
| Fleet | +1.7% | £12.0k | £17.1k | £1.9kᶠ | £12.71m | -3.8% | £2.1k |
Companion convention: active-MW-days run continuously from each unit's first metered-volume quarter (commissioning) to the window end — idle quarters count as in-denominator downtime — and CM accrual realigns to the same entrant dates (numerators unchanged). First-metered entrants: 2025Q3: 13 units / 739 MW (13.4%) · 2025Q4: 14 units / 545 MW (9.0%) · 2026Q1: 9 units / 288 MW (4.6%) · 2026Q2: 7 units / 256 MW (4.0%); re-entries after an idle quarter (returns, not commissioning: 57 MW in 2025Q3, 57 MW in 2026Q2) are shown separately from entrants (corrections record, page 5). Resolution: sub-quarter first-metered dates are not derivable from the pinned per-BMU quarter caches, so this companion realigns at quarter resolution; the day-level proration lands with the 2026Q3 refetch. The realigned CM column gives the 4h class the consistent per-MW/yr the published basis withholds (numerator and denominator now cover the same days).
| Class | N | daily top−bottom MID spread £/MWh |
measured capture |
captured £/MWh |
context £/MW·yr |
settlement floorᶠ £/MW·yr |
|---|---|---|---|---|---|---|
| 1h | 1h | £68.23 | 26.5% | £18.11 | ≈ £6.6k | £1.5k |
| 2h | 2h | £64.36 | 24.3% | £15.64 | ≈ £11.4k | £5.3k |
| 4h | 4h | £56.73 | 25.4% | £14.43 | ≈ £21.1k | £5.9k |
Explicitly not a settlement measurement. Per class: the mean daily top-Nh-minus-bottom-Nh MID spread (N = class duration hours; MID both providers, volume-weighted) × the measured class spread-capture rate, annualised at one cycle/day (× N MWh per MW per day × 365) — published beside the settlement floor as market-comparable context. The gap between this line and the floorᶠ is the measured size of the metered-at-MID convention, not extra revenue; the capture rate's available-spread convention (daily max−min period) is disclosed in the evidence JSON.
Pre-registered 2026-07-23, before any data was fetched for it; applies at the 2026Q3 window advance only, never retroactively; dual-published beside the outgoing basis for at least four quarters. Everything on this page is COMPANION machinery — the graded basis (the published index, its targets and its grades) is unchanged. Two rules act here: a behavioural battery gate (a unit enters companion numerators and MW-day denominators only if its trailing discharge/charge ratio sits in 0.50–1.02; the two-sided sensitivity is on page 5) and metered-implied duration (the p99.5 contiguous-discharge run, page 4) as the primary classification. Gate failures are unclassed — hybrid-suspect units never enter a class row.
| companion — gated, implied duration | current basis (CM band) | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Class | n | MW | BM | FR | WSᶠ | CM | Total | MW | Total |
| 1h | 65 | 2,447 | £5.1k | £26.5k | £-0.1kᶠ | £1.5k | ≥ £33.1k | 1,344 | ≥ £34.2k |
| 2h | 78 | 3,351 | £17.0k | £10.7k | £4.2kᶠ | £2.7k | ≥ £34.7k | 1,773 | ≥ £33.1k |
| 4h | 2 | 45 | £50.3k | £1.6k | £8.1kᶠ | —† | ≥ £60.0k | 313 | ≥ £10.2k |
Same streams, same conventions, same pinned settlement data — only membership (gate + widening) and classification move. n = latest-quarter unit count. † CM per-MW/yr withheld for partial-window classes (same refusal rule as the current basis). The implied cut brings 64 previously un-banded gated-in units (2,886 MW) into the class split, and moves 15 CM-banded units (689 MW) to a different class than their registration. Like-for-like continuity (reclassifying only the CM-banded universe, before the gate): 1h and 2h totals land 1.6% apart (≥ £31.7k vs ≥ £32.2k/MW·yr) — the within-2% fact from page 4, reproduced by this build. Gated fleet, three measured streams: ≥ £32.0k/MW·yr vs ≥ £31.5k on the current basis.
| Unit | dis/ch | MW | WSᶠ | BM | FR |
|---|---|---|---|---|---|
| USKMB-2 ᵂ | 0.00 | 58 | £-0.7k | £0.0k | £0.0k |
| USKMB-3 ᵂ | 0.00 | 58 | £-11.1k | £0.0k | £0.0k |
| USKMB-4 ᵂ | 0.00 | 58 | £-1.9k | £0.0k | £0.0k |
| USKMB-5 ᵂ | 0.00 | 58 | £-0.4k | £0.0k | £0.0k |
| ENDRB-1 ᵂ | 0.31 | 57 | £-154.2k | £0.0k | £0.0k |
| SWGTB-1 | 1.05 | 50 | £450.5k | £3127.0k | £254.8k |
| AG-HAB02B | 0.48 | 49 | £-686.0k | £162.6k | £1994.5k |
| AG-NFLX02 | 82.06 | 49 | £2192.9k | £71.0k | £0.7k |
| AG-PFLX02 | 1.60 | 49 | £2548.8k | £-1839.2k | £1246.1k |
| CHICK-1 ᵂ | 5.90 | 48 | £389.1k | £-1.0k | £0.0k |
| WBURB-43 | 0.47 | 31 | £-117.5k | £21.5k | £531.0k |
| AG-ASTK08 | 1.24 | 16 | £454.8k | £319.2k | £0.0k |
| AG-FLX00L | 2.19 | 4 | £158.0k | £7.3k | £89.9k |
| AG-GBL0DN | 0.00 | 2 | £-3211.6k | £25.9k | £44.6k |
| AG-GBL0EN | 0.00 | 2 | £-4706.4k | £9.9k | £14.4k |
| AG-EXE00E | 0.39 | 1 | £-4.5k | £11.7k | £3.7k |
| WISHD-1 ᵂ | 0.00 | 1 | £-84.0k | £0.0k | £0.0k |
17 of 168 active units fail the 0.50–1.02 band (589 MW; window £: £-2784.1k WSᶠ, £1915.8k BM, £4179.7k FR). ∞ = discharge-only (no metered charge). ᵂ = a widened-membership unit. Their revenue leaves numerators AND their MW leaves denominators — the exclusion is symmetric.
Registry entry no longer requires frequency-response auction participation: any Elexon-registered BMU identified as battery storage (register cross-checked against our seed site registry) with metered volume in the window enters the companion universe, subject to the same gate. This window: 11 candidate BMUs (476 MW) found beyond the auction-conditioned registry; 8 carried metered volume (367 MW); 1 passed the behavioural gate (31 MW) and enter the companion numbers above. For widened units: wholesale is the same metered-at-MID floorᶠ, BM is their fetched settlement cashflows, FR is zero by construction (non-participation defines the cohort), and CM is not joined — disclosed, not guessed. The auction-conditioned membership remains the published basis until the 2026Q3 window advance.
Every number on this page recomputes offline from pinned, committed caches (including new per-BMU half-hourly metered caches); the full companion evidence file ships in the data pack.