Source every end use's off-peak high-rate fraction from the cert 🟩

Surface the hot-water (Table 13 / HP-DHW), secondary (direct-acting),
main-2 and ALL_OTHER_USES High-Rate Fractions on CalculatorInputs from
the same Table 12a helpers the SAP cost path uses, so Bill Derivation's
day/night split matches the rating's exactly.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

domain/sap10_calculator/rdsap/cert_to_inputs.py

@@ -2819,6 +2819,76 @@ def _hot_water_fuel_cost_gbp_per_kwh(
     return _fuel_cost_gbp_per_kwh(main, prices)
 
 
+def _hot_water_high_rate_fraction(
+    water_heating_fuel: Optional[int],
+    main: Optional[MainHeatingDetail],
+    tariff: Tariff,
+    *,
+    water_heating_code: Optional[int] = None,
+    inherit_main_for_community_heating: bool = False,
+    cylinder_volume_l: Optional[float] = None,
+    occupancy_n: Optional[float] = None,
+    immersion_single: Optional[bool] = None,
+) -> float:
+    """ADR-0014 Bill Derivation — the hot-water High-Rate Fraction (the day/high-
+    rate share) on an Off-Peak Meter, mirroring `_hot_water_fuel_cost_gbp_per_kwh`
+    branch-for-branch so the bill's day/night HW split matches the rating's:
+
+    - community-heating HW inheriting a (non-electric) main, non-electric HW, or
+      STANDARD tariff → 1.0 (single rate, no split);
+    - HP-DHW (the WHC inherits a PCDB Table 362 heat-pump main) → Table 12a Grid 1
+      WH `ASHP_APP_N` fraction (0.70 at 7-/10-hour);
+    - electric immersion (WHC 903) with a known cylinder + occupancy → the Table
+      13 dual-immersion fraction (§10.5 assumes a DUAL immersion on a dual meter);
+    - any other electric off-peak HW (e.g. heated by a storage main) → 0.0 (the
+      timer charges it wholly at the night/low rate)."""
+    if inherit_main_for_community_heating:
+        return 1.0
+    if not _is_electric_water(water_heating_fuel) or tariff is Tariff.STANDARD:
+        return 1.0
+    if (
+        water_heating_code in _WATER_INHERIT_FROM_MAIN_CODES
+        and main is not None
+        and main.main_heating_index_number is not None
+        and heat_pump_record(main.main_heating_index_number) is not None
+    ):
+        return water_heating_high_rate_fraction(Table12aSystem.ASHP_APP_N, tariff)
+    if (
+        water_heating_code == _WHC_ELECTRIC_IMMERSION
+        and cylinder_volume_l is not None
+        and occupancy_n is not None
+    ):
+        effective_single = (
+            immersion_single if immersion_single is not None else False
+        )
+        return electric_dhw_high_rate_fraction(
+            cylinder_volume_l=cylinder_volume_l,
+            occupancy_n=occupancy_n,
+            single_immersion=effective_single,
+            tariff=tariff,
+        )
+    return 0.0
+
+
+def _secondary_high_rate_fraction(epc: EpcPropertyData, tariff: Tariff) -> float:
+    """ADR-0014 Bill Derivation — the secondary-heating High-Rate Fraction on an
+    Off-Peak Meter. Non-electric or standard-tariff secondary → 1.0. Electric
+    secondary heaters are portable/direct-acting (Table 4a room heaters), so they
+    take the Table 12a Grid 1 `OTHER_DIRECT_ACTING_ELECTRIC` row (1.0 at 7-hour,
+    0.50 at 10-hour) — run on demand, mostly at the day/high rate. Tariffs Table
+    12a omits (18-/24-hour) fall back to 1.0 (high)."""
+    if tariff is Tariff.STANDARD:
+        return 1.0
+    if not is_electric_fuel_code(_secondary_fuel_code(epc)):
+        return 1.0
+    try:
+        return space_heating_high_rate_fraction(
+            Table12aSystem.OTHER_DIRECT_ACTING_ELECTRIC, tariff
+        )
+    except NotImplementedError:
+        return 1.0
+
+
 def _secondary_fraction(
     main: Optional[MainHeatingDetail],
     secondary_heating_type: object,
@@ -3408,6 +3478,27 @@ def _other_fuel_cost_gbp_per_kwh(
     return blended * _PENCE_TO_GBP
 
 
+def _other_uses_high_rate_fraction(tariff: Tariff) -> float:
+    """ADR-0014 Bill Derivation — the ALL_OTHER_USES High-Rate Fraction (the
+    day/high-rate share) for lighting / appliances / cooking / pumps on an
+    Off-Peak Meter, mirroring `_other_fuel_cost_gbp_per_kwh`'s tariff handling so
+    the bill's split matches the rating's: STANDARD → 1.0 (single rate); 7-/10-
+    hour → SAP 10.2 Table 12a Grid 2; 18-hour → 1.0 (all other uses bill at the
+    high rate per SAP 10.2 Appendix F2); 24-hour → 1.0 (a heating-only tariff —
+    the Fuel Rates snapshot carries no separate non-heating rate, so other uses
+    bill at the off-peak day rate, a documented approximation for a rare tariff).
+
+    Pumps/fans reuse this fraction; the Table 12a Grid 2 MEV/MVHR `FANS_FOR_MECH_
+    VENT` distinction the SAP cost path applies is a small second-order effect on
+    a small load and is deferred for the bill."""
+    if tariff is Tariff.STANDARD:
+        return 1.0
+    try:
+        return other_use_high_rate_fraction(OtherUse.ALL_OTHER_USES, tariff)
+    except NotImplementedError:
+        return 1.0
+
+
 def _pumps_fans_fuel_cost_gbp_per_kwh(
     *,
     tariff: Tariff,
@@ -8164,6 +8255,28 @@ def cert_to_inputs(
     _main_high_rate_fraction = _main_space_heating_high_rate_fraction(
         main, _billing_tariff
     )
+    _main_2_detail = (
+        epc.sap_heating.main_heating_details[1]
+        if epc.sap_heating and len(epc.sap_heating.main_heating_details) > 1
+        else None
+    )
+    _main_2_high_rate_fraction = _main_space_heating_high_rate_fraction(
+        _main_2_detail, _billing_tariff
+    )
+    _secondary_high_rate_frac = _secondary_high_rate_fraction(epc, _billing_tariff)
+    _hw_high_rate_fraction = _hot_water_high_rate_fraction(
+        _water_heating_fuel_code(epc),
+        _water_heating_main(epc),
+        _billing_tariff,
+        water_heating_code=(
+            epc.sap_heating.water_heating_code if epc.sap_heating else None
+        ),
+        inherit_main_for_community_heating=_is_community_heating_hw_from_main(epc),
+        cylinder_volume_l=_hot_water_cylinder_volume_l(epc),
+        occupancy_n=wh_result.occupancy if wh_result is not None else None,
+        immersion_single=_immersion_is_single(epc),
+    )
+    _other_uses_fraction = _other_uses_high_rate_fraction(_billing_tariff)
 
     return CalculatorInputs(
         dimensions=dim,
@@ -8231,6 +8344,11 @@ def cert_to_inputs(
         hot_water_fuel_code=_water_heating_fuel_code(epc),
         is_off_peak_meter=_is_off_peak_meter,
         main_heating_high_rate_fraction=_main_high_rate_fraction,
+        main_2_heating_high_rate_fraction=_main_2_high_rate_fraction,
+        secondary_heating_high_rate_fraction=_secondary_high_rate_frac,
+        hot_water_high_rate_fraction=_hw_high_rate_fraction,
+        pumps_fans_high_rate_fraction=_other_uses_fraction,
+        other_electricity_high_rate_fraction=_other_uses_fraction,
         space_heating_fuel_cost_gbp_per_kwh=_space_heating_fuel_cost_gbp_per_kwh(
             main, _rdsap_tariff(epc), prices
         ),

tests/domain/sap10_calculator/rdsap/test_cert_to_inputs.py

@@ -870,6 +870,10 @@ def test_off_peak_storage_cert_surfaces_billing_meter_flag_and_main_fraction() -
     # Assert — whole-meter off-peak, main heating high-rate fraction 0.20.
     assert inputs.is_off_peak_meter is True
     assert inputs.main_heating_high_rate_fraction == 0.20
+    # Lighting / appliances / cooking + pumps bill at the 7-hour Table 12a
+    # Grid 2 ALL_OTHER_USES high-rate fraction (0.90), mostly at the day rate.
+    assert inputs.other_electricity_high_rate_fraction == 0.90
+    assert inputs.pumps_fans_high_rate_fraction == 0.90
 
 
 def test_off_peak_immersion_unlodged_type_defaults_to_dual_table13_blend() -> None:
@@ -919,6 +923,14 @@ def test_off_peak_immersion_unlodged_type_defaults_to_dual_table13_blend() -> No
     rate = inputs.hot_water_fuel_cost_gbp_per_kwh
     assert rate > 0.0550 + 1e-6   # NOT the 100%-low-rate bug value (5.50 p/kWh)
     assert rate < 0.0900          # a small DUAL high-rate fraction, not single (~11 p)
+    # ADR-0014 Bill Derivation surfaces the SAME Table 13 fraction it bills the
+    # HW cost at: a small day-rate share (0 < frac < 0.3), not 0.0 (all-night
+    # fallback) nor 1.0 (single rate). Mirrors the cost-rate split exactly.
+    assert 0.0 < inputs.hot_water_high_rate_fraction < 0.3
+    # Back out the fraction the cost rate used and confirm the surfaced one
+    # matches it: rate_p = frac×15.29 + (1−frac)×5.50.
+    _frac_from_cost = (rate * 100.0 - 5.50) / (15.29 - 5.50)
+    assert inputs.hot_water_high_rate_fraction == pytest.approx(_frac_from_cost)
 
 
 def test_non_integrated_storage_heater_bills_100_percent_low_rate() -> None: