Model/domain
Khalim Conn-Kowlessar 39ae2cf0c2 fix(water-heating): split whc-903 immersion HW CO2/PE on off-peak tariffs
SAP 10.2 Table 12d/12e: electric water heating on a 7-/10-hour tariff bills
CO2/PE at the high-rate code (32/34) and low-rate code (31/33), kWh-weighted
by the Table 13 high-rate fraction. The cost path already applied this split;
the CO2/PE factors did not — they used the flat annual Table 12 figure
(0.136 CO2 / 1.501 PE) for ALL dual-rate electric HW.

That flat-annual behaviour (slice S0380.163) was validated only against
HW-from-main "low-rate cost" certs (100% low, no high-rate split). It is NOT
how Elmhurst bills a whc-903 ELECTRIC IMMERSION: the hand-built case-50
worksheet (000565 + dual immersion, 7-hour) splits HW CO2/PE into "high rate
cost" (CO2 0.1475 / PE 1.5514) + "low rate cost" (CO2 0.1238 / PE 1.4429)
weighted by the Table 13 fraction 0.1009. So flat-0.136 for immersion HW was
a spec gap on our side, not an Elmhurst divergence.

Fix: `_electric_immersion_hw_high_rate_fraction` threads the Table 13 fraction
(scoped to whc-903, 7-/10-hour, cylinder data present) into the HW CO2 + PE
factor helpers, which then blend the Table 12d/12e high/low codes. The flat
rule is unchanged for HW-from-main and 18-/24-hour (no Table 12d split), so
the S0380.163 41-variant cases and the existing pin are untouched.

Case 50: rating CO2 2413.48 -> 2397.1237 = Elmhurst EXACT; demand CO2 2007.1384
EXACT; demand PE +111 -> +32.5 residual (within corpus PE noise). Corpus
unchanged 73.3% / MAE 0.774 / CO2 0.08 / PE 3.4 (62 whc-903 off-peak certs;
aggregate gauges hold). SAP unaffected (cost-based).

Pin: test_whc903_immersion_hw_co2_pe_factors_split_high_low_on_off_peak; doc
updated in SAP_CALCULATOR.md §8.1.
pyright strict gate not run locally (pyright not installed in this container).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-06-24 09:05:21 +00:00
..
addresses standardist Address 2026-05-22 10:13:32 +00:00
billing feat(modelling): attribute per-measure bill savings via a telescoping cascade 2026-06-03 18:01:11 +00:00
data_transformation moved classifier data transformation to an easy one 2026-06-01 14:53:34 +00:00
epc move overlas to its own thing 2026-06-18 10:04:14 +00:00
epc_prediction refactor(epc-prediction): PR review — rename ComparableProperty, relocate PredictionTarget 2026-06-16 13:34:44 +00:00
fuel_rates feat(fuel-rates): FuelRates snapshot + repository foundation (ADR-0014) 2026-06-02 09:29:07 +00:00
geospatial feat(geospatial): one-read spatial reference (coords + restrictions) 2026-06-04 17:13:39 +00:00
magicplan add todo comment for named ranges 2026-06-10 13:32:11 +00:00
modelling Overlay landlord property-type and built-form corrections onto the Effective EPC 🟩 2026-06-17 18:06:29 +00:00
property Fold landlord overrides onto the lodged EPC to form the Effective EPC 🟩 2026-06-16 17:18:31 +00:00
property_baseline feat(baseline): sap_code_to_fuel normalizes via the calculator's own helper 2026-06-05 18:59:25 +00:00
sap10_calculator fix(water-heating): split whc-903 immersion HW CO2/PE on off-peak tariffs 2026-06-24 09:05:21 +00:00
sap10_ml fix(uvalues): thread glazing gap into pre-2002 window U fallback (RdSAP 10 Table 24, PDF p.50) 2026-06-20 14:14:31 +00:00
tasks added postcode splitter rewrite to ddd 2026-05-19 16:35:09 +00:00
building_geometry.py feat(modelling): floor Recommendation Generator + ground-floor-area geometry 2026-06-03 09:12:29 +00:00
postcode.py get rid of comments 2026-05-20 13:21:11 +00:00