Merge pull request #1363 from Hestia-Homes/fix/hyde-portfolio-audit

fix(full-sap): seven mapper/overlay fixes from the portfolio-796 modelling audit

datatypes/epc/domain/mapper.py

@@ -866,7 +866,10 @@ class EpcPropertyDataMapper:
             # explicit flag); tariff → meter_type; wind turbines pass through.
             sap_energy_source=SapEnergySource(
                 mains_gas=_sap_dwelling_on_mains_gas(schema),
-                meter_type=str(schema.sap_energy_source.electricity_tariff or ""),
+                meter_type=_sap_17_1_meter_type(
+                    schema.sap_energy_source.electricity_tariff
+                ),
+                photovoltaic_arrays=_sap_17_1_pv_arrays(schema),
                 pv_battery_count=0,
                 wind_turbines_count=schema.sap_energy_source.wind_turbines_count or 0,
                 gas_smart_meter_present=False,
@@ -2932,6 +2935,59 @@ def _sap_dwelling_on_mains_gas(schema: SapSchema17_1) -> bool:
     )
 
 
+def _sap_17_1_pv_arrays(
+    schema: SapSchema17_1,
+) -> Optional[List[PhotovoltaicArray]]:
+    """Map a full-SAP cert's lodged PV (`sap_energy_source.pv_arrays`) to the
+    domain `PhotovoltaicArray` list the calculator's Appendix-M generation
+    credit reads. Without this the PV is dropped and an all-electric dwelling
+    that the array lifts to A/B is mis-modelled down a band or more. An array
+    with no peak power generates nothing, so it's skipped; orientation honours
+    the ND/NA sentinel (None ⇒ zero-generation array)."""
+    arrays = schema.sap_energy_source.pv_arrays
+    if not arrays:
+        return None
+    mapped = [
+        PhotovoltaicArray(
+            peak_power=array.peak_power,
+            pitch=array.pitch if array.pitch is not None else 0,
+            overshading=array.overshading if array.overshading is not None else 0,
+            orientation=_pv_orientation(array.orientation),
+        )
+        for array in arrays
+        if array.peak_power is not None
+    ]
+    return mapped or None
+
+
+def _sap_17_1_meter_type(electricity_tariff: Optional[int]) -> str:
+    """Translate a full-SAP ``energy_tariff`` code into the RdSAP ``meter_type``
+    value the calculator's Table 12a tariff resolver consumes.
+
+    The two code spaces *differ* (epc_codes.csv `energy_tariff` vs
+    `_METER_INT_TO_TARIFF`): full-SAP 1=standard / 2=off-peak-7hr / 3=off-peak-
+    10hr / 4=24-hour, whereas RdSAP meter 1=dual-7hr / 2=single / 3=unknown /
+    4=24-hour. Passing the full-SAP code straight through (the prior bug) read a
+    standard-tariff cert as Economy 7 (over-rated) and an Economy-7 cert as
+    single (under-rated). Map onto the RdSAP word aliases so the resolved tariff
+    is correct; absent/ND → "" (the unknown→standard sentinel)."""
+    if electricity_tariff is None:
+        return ""
+    return _SAP_TARIFF_TO_RDSAP_METER_TYPE.get(electricity_tariff, "")
+
+
+# full-SAP `energy_tariff` code → RdSAP `meter_type` word alias (consumed by
+# `tariff_from_meter_type` / `_METER_STR_TO_INT`). 10-hour (3) has no dedicated
+# RdSAP meter code — it maps to "dual", and the §12 dispatch resolves 7-/10-hour
+# from the heating system.
+_SAP_TARIFF_TO_RDSAP_METER_TYPE: dict[int, str] = {
+    1: "single",          # standard tariff
+    2: "dual",            # off-peak 7 hour (Economy 7)
+    3: "dual",            # off-peak 10 hour (§12 dispatch resolves 7/10hr)
+    4: "dual (24 hour)",  # 24-hour tariff
+}
+
+
 def _sap_17_1_heating(schema: SapSchema17_1) -> SapHeating:
     """D6: map full-SAP `sap_heating` onto the domain `SapHeating`. Field names
     differ from RdSAP — `is_flue_fan_present`→`fan_flue_present`,

datatypes/epc/domain/tests/test_from_sap_schema.py

@@ -137,6 +137,67 @@ class TestFromSapSchema17_1RebaselineFields:
         assert result.assessment_type == "SAP"
 
 
+class TestFullSapPhotovoltaics:
+    """Full-SAP certs lodge measured PV under `sap_energy_source.pv_arrays`;
+    the mapper must carry it to the domain `photovoltaic_arrays` so the
+    Appendix-M generation credit isn't silently dropped."""
+
+    def test_maps_the_lodged_pv_array(self) -> None:
+        # sap_17_1_house.json lodges one 1.62 kWp array (pitch 3, orientation 6,
+        # overshading 1).
+        schema = from_dict(SapSchema17_1, load("sap_17_1_house.json"))
+
+        result = EpcPropertyDataMapper.from_sap_schema_17_1(schema)
+
+        arrays = result.sap_energy_source.photovoltaic_arrays
+        assert arrays is not None
+        assert len(arrays) == 1
+        assert arrays[0].peak_power == 1.62
+
+
+class TestFullSapElectricityTariffTranslation:
+    """The full-SAP `energy_tariff` code space differs from the RdSAP
+    `meter_type` one the calculator reads, so the mapper must translate it."""
+
+    def test_economy7_tariff_is_not_read_as_single_rate(self) -> None:
+        # full-SAP energy_tariff 2 = "off-peak 7 hour" (Economy 7). Passing the
+        # code straight through read it as RdSAP meter 2 = Single → no off-peak
+        # split (under-rated). It must resolve to the SEVEN_HOUR off-peak tariff.
+        from domain.sap10_calculator.tables.table_12a import (
+            Tariff,
+            tariff_from_meter_type,
+        )
+
+        from datatypes.epc.domain.mapper import _sap_17_1_meter_type
+
+        meter_type = _sap_17_1_meter_type(2)
+
+        assert tariff_from_meter_type(meter_type) is Tariff.SEVEN_HOUR
+
+    @pytest.mark.parametrize(
+        ("energy_tariff", "expected"),
+        [
+            (1, "STANDARD"),         # standard tariff → single-rate (was over-rated as E7)
+            (2, "SEVEN_HOUR"),       # off-peak 7-hour → Economy 7
+            (3, "SEVEN_HOUR"),       # off-peak 10-hour → dual (§12 resolves 7/10hr)
+            (4, "TWENTY_FOUR_HOUR"),  # 24-hour tariff (e.g. property 709874 — unchanged)
+            (None, "STANDARD"),      # absent/ND → unknown → standard
+        ],
+    )
+    def test_energy_tariff_resolves_to_the_correct_calculator_tariff(
+        self, energy_tariff: Any, expected: str
+    ) -> None:
+        from domain.sap10_calculator.tables.table_12a import (
+            tariff_from_meter_type,
+        )
+
+        from datatypes.epc.domain.mapper import _sap_17_1_meter_type
+
+        resolved = tariff_from_meter_type(_sap_17_1_meter_type(energy_tariff))
+
+        assert resolved.name == expected
+
+
 class TestFromSapSchema17_1DisplayElements:
     """Display EnergyElements the WIP mapper dropped, leaving the FE
     property-details panel "Unknown" for full-SAP certs (ADR-0037). Brings
@@ -671,8 +732,9 @@ class TestFromSapSchema16_2:
         epc = EpcPropertyDataMapper.from_api_response(load("sap_17_0.json"))
         assert isinstance(epc, EpcPropertyData)
         assert epc.uprn == 10023444324
-        # lodged 82; engine produces 80.
-        assert Sap10Calculator().calculate(epc).sap_score == 80
+        # lodged 82; the engine now also produces 82 — the cert's lodged PV is
+        # credited (previously dropped by the full-SAP mapper, under-rating to 80).
+        assert Sap10Calculator().calculate(epc).sap_score == 82
 
     def test_18_0_0_dispatches_via_full_sap_path(self) -> None:
         # SAP-Schema-18.0.0 is the full-SAP 17.1 shape; dispatched to

datatypes/epc/schema/sap_schema_17_1.py

@@ -107,6 +107,20 @@ class SapVentilation:
     mechanical_vent_duct_type: Optional[int] = None
 
 
+@dataclass
+class SapPvArray:
+    """One measured photovoltaic array lodged on a full-SAP cert (under
+    `sap_energy_source.pv_arrays`): peak power (kWp), pitch, SAP octant
+    orientation (1-8), overshading code, and the connection type. Mirrors the
+    domain `PhotovoltaicArray` the calculator's Appendix M generation uses."""
+
+    peak_power: Optional[float] = None
+    pitch: Optional[int] = None
+    orientation: Optional[int] = None
+    overshading: Optional[int] = None
+    pv_connection: Optional[int] = None
+
+
 @dataclass
 class SapEnergySource:
     """Electricity tariff, on-site generation and lighting. Lighting outlet
@@ -118,6 +132,7 @@ class SapEnergySource:
     wind_turbine_terrain_type: Optional[int] = None
     fixed_lighting_outlets_count: Optional[int] = None
     low_energy_fixed_lighting_outlets_count: Optional[int] = None
+    pv_arrays: Optional[List[SapPvArray]] = None
 
 
 @dataclass

domain/epc/property_overlays/main_heating_system_overlay.py

@@ -12,10 +12,11 @@ field-wise with the main_fuel / water_heating overlays.
 electricity tariff (meter) and, for storage heaters, its charge control. Rather
 than hand-attach those per archetype (easy to forget when a new system is
 added), they are **derived from the SAP code**: the off-peak meter from the
-calculator's single off-peak classification (`OFF_PEAK_IMPLYING_HEATING_CODES`,
-SAP §12), and the conservative manual charge control for storage heaters. So
-adding a heating archetype is just adding its code — coherent companions fall
-out. Synthesis owns coherence; the calculator never normalises a lodged cert.
+overlay's assumed-Dual classification (`_ASSUMED_DUAL_METER_CODES` — the §12
+off-peak systems plus all-electric room-heater dwellings), and the conservative
+manual charge control for storage heaters. So adding a heating archetype is just
+adding its code — coherent companions fall out. Synthesis owns coherence; the
+calculator never normalises a lodged cert.
 
 The SEDBUK A-G efficiency band the Hyde "Heating" column carries is NOT honoured
 yet (no efficiency slot on the overlay/MainHeatingDetail) -- archetypes map to
@@ -45,6 +46,19 @@ _OFF_PEAK_METER = "Dual"
 # split (the mirror of the storage→Dual drag, ADR-0035).
 _SINGLE_RATE_METER = "Single"
 
+# Electric room heaters (SAP Table 4a 691). They don't *require* off-peak the way
+# storage/CPSU do, so they're absent from the calculator's §12
+# `OFF_PEAK_IMPLYING_HEATING_CODES` (Rules 1-2). But a dwelling heated by them is
+# all-electric and realistically billed on Economy 7 — its immersion hot water
+# charges overnight and §12 Rule 3 gives the room heaters a 10-hour off-peak
+# window. So when the landlord names only the system, the coherent meter to
+# assume is Dual; the §12 dispatch then applies the realistic high/low split
+# (not a single-rate over-penalty, nor an all-low over-credit).
+_ROOM_HEATER_CODES = frozenset({691})
+# Codes for which the overlay assumes a Dual (off-peak) meter: the §12-mandated
+# off-peak systems plus the all-electric room-heater dwellings above.
+_ASSUMED_DUAL_METER_CODES = OFF_PEAK_IMPLYING_HEATING_CODES | _ROOM_HEATER_CODES
+
 # SAP Table 4e Group 4 storage charge-control code. Manual charge control is the
 # *conservative* assumption when the landlord didn't tell us the control: its
 # +0.7 C mean-internal-temperature adjustment is the largest of the storage
@@ -80,9 +94,11 @@ _FROM_MAIN_WATER_HEATING_CODE = 901
 # Canonical system archetype → representative SAP `sap_main_heating_code`. Codes
 # map to the modern/condensing variant (A-G efficiency deferred): 102 regular
 # condensing, 104 condensing combi, 120 CPSU, 401-404 storage heaters, 191
-# direct-acting electric. Companion fields (meter / control / fuel / hot water)
-# are NOT listed here — they are derived from the code below, so a new archetype
-# is just a code (ADR-0035 drag-along).
+# direct-acting electric, 691 panel/convector/radiant electric room heaters
+# (Table 4a — direct-acting, so a single-rate meter, NOT off-peak storage).
+# Companion fields (meter / control / fuel / hot water) are NOT listed here —
+# they are derived from the code below, so a new archetype is just a code
+# (ADR-0035 drag-along).
 _MAIN_HEATING_CODES: dict[str, int] = {
     "Gas boiler, combi": 104,
     "Gas boiler, regular": 102,
@@ -92,14 +108,16 @@ _MAIN_HEATING_CODES: dict[str, int] = {
     "Electric storage heaters, convector": 403,
     "Electric storage heaters, fan": 404,
     "Direct-acting electric": 191,
+    "Electric room heaters": 691,
 }
 
 
 def _meter_for(code: int) -> str:
     """The coherent meter a heating code implies: an off-peak ("Dual") meter for
-    the calculator's §12 off-peak systems, an explicit single-rate ("Single")
-    meter for every other system. Always set — never left to bleed."""
-    return _OFF_PEAK_METER if code in OFF_PEAK_IMPLYING_HEATING_CODES else _SINGLE_RATE_METER
+    the §12 off-peak systems and all-electric room-heater dwellings
+    (`_ASSUMED_DUAL_METER_CODES`), an explicit single-rate ("Single") meter for
+    every other system. Always set — never left to bleed."""
+    return _OFF_PEAK_METER if code in _ASSUMED_DUAL_METER_CODES else _SINGLE_RATE_METER
 
 
 def _control_for(code: int) -> Optional[int]:
@@ -146,5 +164,10 @@ def main_heating_overlay_for(
             sap_main_heating_code=code,
             meter_type=_meter_for(code),
             main_heating_control=_control_for(code),
+            # A landlord override describes the existing dwelling, so its assumed
+            # off-peak meter must not downgrade a more-off-peak cert meter
+            # (e.g. a 24-hour all-low tariff). Measures, which re-meter for real,
+            # build their HeatingOverlay directly and leave this False.
+            keep_existing_off_peak_meter=True,
         )
     )

domain/epc/property_overlays/wall_type_overlay.py

@@ -31,6 +31,9 @@ _MATERIAL_CONSTRUCTION: dict[str, int] = {
     "Curtain Wall": 9,
 }
 
+# RdSAP `WALL_SYSTEM_BUILT` — shares code 6 with the gov-EPC basement sentinel.
+_WALL_SYSTEM_BUILT = 6
+
 # RdSAP `wall_insulation_type` codes by insulation-state suffix
 # (domain/sap10_ml/rdsap_uvalues.py): external 1, filled-cavity 2, internal 3,
 # as-built/uninsulated 4, cavity+external 6, cavity+internal 7.
@@ -66,11 +69,18 @@ def wall_overlay_for(
         if building_part == 0
         else BuildingPartIdentifier.extension(building_part)
     )
+    # System-built is RdSAP code 6, which collides with the gov-EPC code-6
+    # basement sentinel that `main_wall_is_basement` falls back to. A landlord
+    # naming a System-built wall is asserting the material, not a basement — pin
+    # the flag False so the override isn't mis-read as one (ADR-0033 / the
+    # overlay mirror of the mapper's `_clear_basement_flag_when_system_built`).
+    wall_is_basement = False if construction == _WALL_SYSTEM_BUILT else None
     return EpcSimulation(
         building_parts={
             identifier: BuildingPartOverlay(
                 wall_construction=construction,
                 wall_insulation_type=insulation,
+                wall_is_basement=wall_is_basement,
             )
         }
     )

domain/epc/property_overrides/main_heating_system_type.py

@@ -24,4 +24,5 @@ class MainHeatingSystemType(Enum):
     ELECTRIC_STORAGE_CONVECTOR = "Electric storage heaters, convector"
     ELECTRIC_STORAGE_FAN = "Electric storage heaters, fan"
     DIRECT_ELECTRIC = "Direct-acting electric"
+    ELECTRIC_ROOM_HEATERS = "Electric room heaters"
     UNKNOWN = "Unknown"

domain/modelling/scoring/overlay_applicator.py

@@ -152,6 +152,22 @@ _SAP_HEATING_FIELDS: tuple[str, ...] = (
 _ENERGY_SOURCE_FIELDS: tuple[str, ...] = ("meter_type", "mains_gas")
 
 
+def _is_off_peak_meter(meter_type: object) -> bool:
+    """True iff the meter resolves to an off-peak Table 12a tariff (not the
+    STANDARD single-rate column). Unparseable / absent meters count as not
+    off-peak so a coherent override meter still applies to them."""
+    from domain.sap10_calculator.exceptions import UnmappedSapCode
+    from domain.sap10_calculator.tables.table_12a import (
+        Tariff,
+        tariff_from_meter_type,
+    )
+
+    try:
+        return tariff_from_meter_type(meter_type) is not Tariff.STANDARD
+    except UnmappedSapCode:
+        return False
+
+
 def _fold_heating(epc: EpcPropertyData, overlay: HeatingOverlay) -> None:
     """Write a `HeatingOverlay`'s non-``None`` fields onto the (copied) dwelling,
     routing each to its home: the primary ``main_heating_details[0]``, the
@@ -181,8 +197,25 @@ def _fold_heating(epc: EpcPropertyData, overlay: HeatingOverlay) -> None:
         epc.has_hot_water_cylinder = overlay.has_hot_water_cylinder
     for field_name in _ENERGY_SOURCE_FIELDS:
         value = getattr(overlay, field_name)
-        if value is not None:
-            setattr(epc.sap_energy_source, field_name, value)
+        if value is None:
+            continue
+        # A landlord heating override's assumed meter (Dual for off-peak
+        # systems) is a coherent default, not a re-metering of the cert: when it
+        # opts in (`keep_existing_off_peak_meter`), don't downgrade a cert that
+        # already lodges a MORE off-peak meter (e.g. a 24-hour all-low tariff) to
+        # the overlay's 7-hour E7 — keep the cert's (more specific) one. Single/
+        # unknown existing meters still receive the off-peak meter, and a switch
+        # to single-rate still resets it (its desired value isn't off-peak).
+        # Heating MEASURES leave the flag False — they re-meter for real
+        # (Elmhurst re-lodges 18-hour → Dual on a storage install).
+        if (
+            field_name == "meter_type"
+            and overlay.keep_existing_off_peak_meter
+            and _is_off_peak_meter(value)
+            and _is_off_peak_meter(epc.sap_energy_source.meter_type)
+        ):
+            continue
+        setattr(epc.sap_energy_source, field_name, value)
 
 
 # `SolarOverlay` fields all live on `sap_energy_source` (the home of the SAP

domain/modelling/simulation.py

@@ -36,6 +36,14 @@ class BuildingPartOverlay:
     construction_age_band: Optional[str] = None
     wall_construction: Optional[int] = None
     wall_insulation_type: Optional[int] = None
+    # Disambiguates the RdSAP `wall_construction == 6` code collision: gov-EPC
+    # code 6 = "Basement wall" but RdSAP `WALL_SYSTEM_BUILT` is also 6, and
+    # `SapBuildingPart.main_wall_is_basement` falls back to the code-6 heuristic
+    # when the flag is `None`. A Landlord Override that sets a System-built wall
+    # (construction 6) must therefore set this `False` so the override isn't
+    # mis-read as a basement — the overlay-path mirror of the gov-API mapper's
+    # `_clear_basement_flag_when_system_built`.
+    wall_is_basement: Optional[bool] = None
     # Added solid-wall insulation depth (mm) — drives the calculator's Table 6
     # bucket / §5.8 documentary U-value for EWI (`wall_insulation_type=1`) and
     # IWI (`wall_insulation_type=3`); λ defaults to 0.04 W/m·K in the calculator.
@@ -185,6 +193,13 @@ class HeatingOverlay:
     # sap_energy_source
     meter_type: Optional[str] = None
     mains_gas: Optional[bool] = None
+    # A landlord heating-system override DESCRIBES the existing dwelling, so its
+    # assumed off-peak (`meter_type`) is a coherent default, not a re-metering:
+    # it must not downgrade a cert that already lodges a MORE off-peak meter
+    # (e.g. a 24-hour all-low tariff → the overlay's 7-hour E7). A heating
+    # MEASURE re-meters for real (Elmhurst re-lodges 18-hour → Dual on a storage
+    # install), so it leaves this False. `_fold_heating` reads it.
+    keep_existing_off_peak_meter: bool = False
 
 
 @dataclass(frozen=True)

tests/domain/epc/test_main_heating_system_overlay.py

@@ -11,12 +11,10 @@ import pytest
 from domain.epc.property_overrides.main_heating_system_type import MainHeatingSystemType
 from domain.epc.property_overlays.main_fuel_overlay import fuel_overlay_for
 from domain.epc.property_overlays.main_heating_system_overlay import (
+    _ASSUMED_DUAL_METER_CODES,
     _MAIN_HEATING_CODES,
     main_heating_overlay_for,
 )
-from domain.sap10_calculator.tables.table_12a import (
-    OFF_PEAK_IMPLYING_HEATING_CODES,
-)
 from domain.epc.property_overlays.water_heating_overlay import (
     water_heating_overlay_for,
 )
@@ -36,6 +34,29 @@ def test_gas_combi_overlays_the_primary_heating_code() -> None:
     assert simulation.heating.sap_main_heating_code == 104
 
 
+def test_electric_room_heaters_overlay_the_direct_acting_room_heater_code() -> None:
+    # Act — panel/convector/radiant direct-acting electric room heaters
+    simulation = main_heating_overlay_for("Electric room heaters", 0)
+
+    # Assert — SAP Table 4a code 691, NOT convector storage (403).
+    assert simulation is not None
+    assert simulation.heating is not None
+    assert simulation.heating.sap_main_heating_code == 691
+
+
+def test_electric_room_heaters_assume_a_dual_economy7_meter() -> None:
+    # A dwelling on electric room heaters is all-electric and realistically
+    # billed on Economy 7 (its immersion hot water charges overnight; §12 Rule 3
+    # gives the room heaters a 10-hour off-peak window). When the landlord names
+    # only the system, the coherent meter to assume is Dual — the §12 dispatch
+    # then applies the realistic high/low split, not a single-rate over-penalty.
+    simulation = main_heating_overlay_for("Electric room heaters", 0)
+
+    assert simulation is not None
+    assert simulation.heating is not None
+    assert simulation.heating.meter_type == "Dual"
+
+
 @pytest.mark.parametrize(
     ("main_heating_value", "code"),
     [
@@ -218,7 +239,7 @@ def test_off_peak_archetypes_drag_dual_others_drag_single() -> None:
     for value, code in _MAIN_HEATING_CODES.items():
         simulation = main_heating_overlay_for(value, 0)
         assert simulation is not None and simulation.heating is not None
-        expected = "Dual" if code in OFF_PEAK_IMPLYING_HEATING_CODES else "Single"
+        expected = "Dual" if code in _ASSUMED_DUAL_METER_CODES else "Single"
         assert simulation.heating.meter_type == expected, value
 
 
@@ -308,6 +329,48 @@ def test_the_three_heating_overrides_compose_without_conflict() -> None:
     assert result.sap_heating.water_heating_fuel == 29
 
 
+def test_room_heaters_preserve_an_existing_more_off_peak_cert_meter() -> None:
+    # The overlay's assumed Dual (7-hour E7) meter is a coherent *default* for a
+    # single/unknown-meter dwelling — it must NOT downgrade a cert that already
+    # lodges a more-off-peak meter (here a 24-hour all-low tariff, code "4").
+    # Clobbering it to E7 would bill the heating on a high/low split it doesn't
+    # have, under-rating the dwelling.
+    baseline = build_epc()
+    baseline.sap_energy_source.meter_type = "4"  # 24-hour tariff
+    overlay = main_heating_overlay_for("Electric room heaters", 0)
+    assert overlay is not None
+
+    result = apply_simulations(baseline, [overlay])
+
+    assert result.sap_energy_source.meter_type == "4"
+
+
+def test_room_heaters_set_dual_when_the_cert_meter_is_single() -> None:
+    # The flip side: a single-rate dwelling DOES get the assumed Dual meter —
+    # off-peak heating can't be billed on a single-rate meter (ADR-0035 drag).
+    baseline = build_epc()
+    baseline.sap_energy_source.meter_type = "Single"
+    overlay = main_heating_overlay_for("Electric room heaters", 0)
+    assert overlay is not None
+
+    result = apply_simulations(baseline, [overlay])
+
+    assert result.sap_energy_source.meter_type == "Dual"
+
+
+def test_electric_room_heaters_member_decodes_to_the_room_heater_code() -> None:
+    # Arrange — the canonical landlord archetype for direct-acting room heaters
+    member = MainHeatingSystemType.ELECTRIC_ROOM_HEATERS
+
+    # Act
+    simulation = main_heating_overlay_for(member.value, 0)
+
+    # Assert — member value stays in lock-step with the overlay (code 691)
+    assert simulation is not None
+    assert simulation.heating is not None
+    assert simulation.heating.sap_main_heating_code == 691
+
+
 @pytest.mark.parametrize(
     "member",
     [m for m in MainHeatingSystemType if m is not MainHeatingSystemType.UNKNOWN],

tests/domain/epc/test_wall_type_overlay.py

@@ -25,6 +25,30 @@ def test_solid_brick_with_internal_insulation_overlays_main_wall() -> None:
     assert overlay.wall_insulation_type == 3
 
 
+def test_system_built_override_is_not_mis_read_as_a_basement() -> None:
+    # A System-built wall is RdSAP code 6, which collides with the gov-EPC
+    # code-6 basement sentinel. The overlay must set wall_is_basement=False so
+    # main_wall_is_basement doesn't fire the code-6 heuristic (phantom basement).
+    simulation = wall_overlay_for(
+        "System built, as built, no insulation (assumed)", 0
+    )
+
+    assert simulation is not None
+    overlay = simulation.building_parts[BuildingPartIdentifier.MAIN]
+    assert overlay.wall_construction == 6
+    assert overlay.wall_is_basement is False
+
+
+def test_non_system_built_override_leaves_basement_flag_untouched() -> None:
+    # Cavity (code 4) can't collide with the basement sentinel, so the overlay
+    # must not assert a basement verdict either way — leave the flag None.
+    simulation = wall_overlay_for("Cavity wall, with internal insulation", 0)
+
+    assert simulation is not None
+    overlay = simulation.building_parts[BuildingPartIdentifier.MAIN]
+    assert overlay.wall_is_basement is None
+
+
 @pytest.mark.parametrize(
     ("wall_type_value", "construction", "insulation"),
     [

tests/domain/epc_prediction/test_component_accuracy_gate.py

@@ -56,6 +56,15 @@ _FIXTURE = Path(__file__).parents[3] / "tests" / "fixtures" / "epc_prediction"
 # new-build-vs-old-stock service mismatch on 1-2 targets each (heating_main_fuel
 # 0.9722->0.9394, water_heating_fuel ->0.9495, cylinder_insulation_type 0.6667->
 # 0.3333) plus floor_area (+0.31 MAE). Tighten-only resumes from these values.
+#
+# has_pv re-baselined 0.9798->0.9697 when full-SAP lodged PV mapping landed
+# (datatypes/epc/domain/mapper.py `_sap_17_1_pv_arrays`): full-SAP certs lodge
+# their measured array under `sap_energy_source.pv_arrays`, which the schema
+# dropped at parse, so the leave-one-out scorer's *actual* has_pv read False for
+# every full-SAP PV dwelling. Carrying the array now reads the true has_pv=True,
+# and one full-SAP target the similarity-weighted donors don't predict as PV
+# tips the agreement 32/33 (the held-out actual is now correct — a ground-truth-
+# method change, not a prediction-logic loosening). Tighten-only resumes here.
 _RATE_FLOORS: dict[str, float] = {
     "wall_construction": 0.9091,
     "wall_insulation_type": 0.8687,
@@ -76,7 +85,7 @@ _RATE_FLOORS: dict[str, float] = {
     "floor_insulation": 0.9375,
     "has_room_in_roof": 0.9495,
     "modal_glazing_type": 0.8384,
-    "has_pv": 0.9798,
+    "has_pv": 0.9697,
     "solar_water_heating": 1.0000,
 }
 

tests/domain/sap10_calculator/test_real_cert_sap_accuracy.py

@@ -122,12 +122,18 @@ _EXPECTATIONS: Final[tuple[RealCertExpectation, ...]] = (
     # (engine uses the cert's measured 0.19/0.11/0.11 U-values; Elmhurst uses
     # age-band L proxies + party-wall default) plus FGHRS (cert idx 60031) omitted
     # on BOTH sides (the engine can't yet model full-SAP FGHRS). PINNED TO THE
-    # OBSERVED 82, not lodged 84 — mapping deliberately untuned.
+    # OBSERVED 83 (was 82), not lodged 84 — mapping deliberately untuned.
+    # WAS 82 until the full-SAP electricity-tariff → RdSAP meter_type fix: this
+    # cert lodges energy_tariff=1 (standard), which the mapper previously passed
+    # through untranslated as RdSAP meter_type "1" — wrongly read as dual/Economy 7
+    # and priced on the off-peak high/low split. Translating it to "single" (the
+    # correct standard tariff) re-prices its electricity at the flat rate, lifting
+    # this gas semi 82→83. No PV (sap_energy_source.pv_arrays absent).
     RealCertExpectation(
         schema="SAP-Schema-17.1",
         sample="uprn_10093116528",
         cert_num="8000-8495-2839-2607-9683",
-        sap_score=82,
+        sap_score=83,
     ),
     # UPRN 10093116543 → cert 8358-7436-5620-6889-0906. SAP-Schema-17.1 — a
     # FULL-SAP cert (2017 mains-gas COMBI semi, Emsworth), forced through the
@@ -290,13 +296,18 @@ _EXPECTATIONS: Final[tuple[RealCertExpectation, ...]] = (
     # control 2106 (CBE); water from primary (combi); MEV on; AP50 Blower Door 3.5.
     # The −3 vs lodged 85 is the documented full-SAP→RdSAP gap: the engine uses the
     # cert's MEASURED U (wall 0.24 / floor 0.13, WORSE than RdSAP band-M defaults)
-    # + MEV priced as extract loss not heat recovery. PINNED to the observed 82 —
-    # mapping untuned; engine == Elmhurst.
+    # + MEV priced as extract loss not heat recovery. PINNED to the observed 84
+    # (was 82), still −1 vs lodged 85 — mapping untuned.
+    # WAS 82 until full-SAP lodged PV mapping landed: this cert lodges a 0.38 kWp
+    # array under sap_energy_source.pv_arrays (SE-facing, pitch 30°, unshaded) that
+    # the schema dropped at parse, so the Appendix-M generation credit was lost.
+    # Carrying it (mapper `_sap_17_1_pv_arrays`) credits the generation and lifts
+    # this flat 82→84, closing most of the gap to the lodged 85 the array explains.
     RealCertExpectation(
         schema="SAP-Schema-19.1.0",
         sample="uprn_10096028301",
         cert_num="0390-3321-6060-2405-7985",
-        sap_score=82,
+        sap_score=84,
     ),
     # UPRN 44012843 → cert 0775-2898-6628-9594-8005. SAP-Schema-16.3 — a
     # reduced-field (RdSAP-shaped) ground-floor FLAT, band K (2007-2011), cavity
@@ -326,14 +337,20 @@ _EXPECTATIONS: Final[tuple[RealCertExpectation, ...]] = (
     # worksheet SAP 80 — engine EXACTLY matches (80.13 vs 80); engine-on-Elmhurst's-
     # own-parsed-inputs 81.03 ≈ 80 → calculator faithful. Boiler set to the cert's
     # exact PCDB 16211 via the search dialog; control 2106 (CBE); water from primary
-    # (combi); MEV on; AP50 Blower Door 3.2; party wall 6.43 m entered. The −2 vs
-    # lodged 82 is the documented full-SAP→RdSAP gap (measured U 0.2/0.1 + MEV
-    # extract loss). PINNED to the observed 80 — mapping untuned; engine == Elmhurst.
+    # (combi); MEV on; AP50 Blower Door 3.2; party wall 6.43 m entered.
+    # WAS 80 (engine == Elmhurst, both built WITHOUT PV) until full-SAP lodged PV
+    # mapping landed: this cert lodges a 0.48 kWp array under
+    # sap_energy_source.pv_arrays (SE-facing, pitch 30°, unshaded) the schema
+    # dropped at parse. Crediting it (mapper `_sap_17_1_pv_arrays`) closes the
+    # −2 gap exactly — the engine now reproduces the accredited lodged 82. The
+    # Elmhurst worksheet (80) omitted the PV (not entered in the RdSAP build), so
+    # the +2 over Elmhurst is the now-credited array, not a calculator drift.
+    # PINNED to the observed 82 == lodged 82 — mapping untuned.
     RealCertExpectation(
         schema="SAP-Schema-17.0",
         sample="uprn_10023444324",
         cert_num="8501-5064-6739-1407-0163",
-        sap_score=80,
+        sap_score=82,
     ),
     # UPRN 10023444320 → cert 0868-6045-7331-4376-0914. SAP-Schema-17.0 — FULL-SAP
     # MID-FLOOR FLAT (sibling of 10023444324, same block / combi PCDB 16211 / MEV),
@@ -342,12 +359,24 @@ _EXPECTATIONS: Final[tuple[RealCertExpectation, ...]] = (
     # worksheet 82 — engine within ~1 (81.38 vs 82); engine-on-Elmhurst-inputs 82.46
     # ≈ 82 → calculator faithful. Boiler PCDB 16211 via search; control 2106 (CBE);
     # water from primary (combi); MEV on; AP50 Blower Door 3.09; mid-floor (floor =
-    # another dwelling below). PINNED to the observed 81 — mapping untuned.
+    # another dwelling below).
+    # WAS 81 until full-SAP lodged PV mapping landed: this cert lodges the SAME
+    # 0.48 kWp array as its ground-floor sibling 10023444324 under
+    # sap_energy_source.pv_arrays (the block's roof PV apportioned to the flat on
+    # the lodged cert). Crediting it faithfully (mapper `_sap_17_1_pv_arrays`)
+    # lifts this flat 81→83. NOTE this lands +2 OVER the lodged 81 (and +1 over the
+    # Elmhurst worksheet 82) — unlike the ground-floor sibling whose pre-PV engine
+    # was 2 UNDER lodged so the same array closed the gap exactly. The mid-floor's
+    # pre-PV engine already matched lodged, so the credited array now overshoots:
+    # the lodged 81 does not appear to carry the array's full generation credit
+    # that SAP Appendix-M awards it. This is the documented full-SAP→RdSAP residual
+    # (faithful to the cert's lodged PV, not tuned to the lodged integer). PINNED
+    # to the observed 83 — mapping untuned.
     RealCertExpectation(
         schema="SAP-Schema-17.0",
         sample="uprn_10023444320",
         cert_num="0868-6045-7331-4376-0914",
-        sap_score=81,
+        sap_score=83,
     ),
     # UPRN 10090844932 → cert 0646-3008-6208-0619-6204. RdSAP-Schema-20.0.0 —
     # END-TERRACE HOUSE, 2-storey, band L (2012-2022), cavity insulated, pitched