Apply the deep-research off-gas figures so oil/smokeless/wood sit on the
same NEP-Apr-2026 retail / DESNZ DUKES gross-CV basis as the new coal
proxy (fuel-input, not useful-heat): OIL 9.16 -> 12.11 (prior value was
materially low vs current kerosene), SMOKELESS 10.0 -> 8.69, WOOD_LOGS
8.83 -> 8.25, WOOD_PELLETS 7.99 -> 7.38. SEG (15.0, Solar Energy UK) and
LPG (17.61, bottled-propane) kept; gas/electricity (Ofgem cap) unchanged.
CV arithmetic recorded in the snapshot _assumptions. OIL pin updated.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Coal and heat networks have no national retail/cap rate, so the snapshot
left them null and BillDerivation raised UnpricedFuel — dropping those
certs from an offline cohort run. Add researched proxy rates (fuel-input
basis, sources + arithmetic in the JSON _note/_gaps): COAL 7.13 p/kWh
(NEP Nov 2025 coal uprated + DESNZ DUKES house-coal GCV) and HEAT_NETWORK
16.0 p/kWh + 69.4 p/day (Insite Energy operator sample; indicative, schemes
vary ~8-30). Both flagged proxy/indicative — sense-check estimates, not
market rates. Existing curated fuels are unchanged.
Replaces the unpriced-raises pin for these two with a positive rate pin;
off-peak stays unpriced pending the day/night accessor. Golden cohort now
runs 57/57 offline with zero errors.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Slice 1 of Bill Derivation — the reference-data foundation that later slices
price the calculator's per-end-use kWh against:
- Fuel enum (canonical billing fuels; the join key between the calculator's
SAP-code fuels and the rates snapshot). COAL + HEAT_NETWORK are members with
no national rate.
- FuelRates value object: unit_rate_p_per_kwh / standing_charge_p_per_day /
seg_export_p_per_kwh; raises UnpricedFuel on a fuel it has no rate for rather
than billing at a wrong default.
- FuelRatesRepository port (ADR-0011 Repo-reads-stored-reference-data) +
StaticFileFuelRatesRepository reading a committed JSON snapshot.
- Snapshot fuel_rates_2026_q2.json: GB national, Apr-Jun 2026 Ofgem cap
(gas/electricity) + DESNZ/NEP May 2026 (off-gas). Carries the full researched
data; the value object exposes single-rate fuels this slice. Off-peak
(day/night), house coal and heat network raise UnpricedFuel until later slices.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
