test(accuracy): pin code-195 electric storage-boiler certs as spec-faithful (§12 Rule 2)

Electric-tariff cluster investigation. The 112-cert electric-main cohort is
mixed-sign within every category/meter - no systematic tariff bias. Root cause
of the biggest non-xfail divergences (10012334488 +13.2, 10091578598 +7.81):
SAP code 195 = 'Electric water storage boiler' (Table 4a p.170), which SAP 10.2
§12 Rule 2 correctly bills mostly at the 7-hour off-peak rate. Both are pure
cost gaps (PE/CO2 match lodged -> demand right); the lodged software over-billed
the storage boilers at peak rate. The engine is SPEC-FAITHFUL - matching lodged
would tune against §12/Table-4a. Pinned to the spec-faithful engine values.

Adds scripts/corpus_1000/elec_cohort.py (electric-main cohort analyzer).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/epc_api/json_samples/real_life_examples/RdSAP-Schema-21.0.1/uprn_10012334488/epc.json

@@ -0,0 +1,337 @@
+{
+  "uprn": 10012334488,
+  "roofs": [
+    {
+      "description": "(another dwelling above)",
+      "energy_efficiency_rating": 0,
+      "environmental_efficiency_rating": 0
+    }
+  ],
+  "walls": [
+    {
+      "description": "System built, as built, insulated (assumed)",
+      "energy_efficiency_rating": 4,
+      "environmental_efficiency_rating": 4
+    }
+  ],
+  "floors": [
+    {
+      "description": "(another dwelling below)",
+      "energy_efficiency_rating": 0,
+      "environmental_efficiency_rating": 0
+    }
+  ],
+  "status": "entered",
+  "tenure": 3,
+  "window": {
+    "description": "Fully double glazed",
+    "energy_efficiency_rating": 3,
+    "environmental_efficiency_rating": 3
+  },
+  "lighting": {
+    "description": "Excellent lighting efficiency",
+    "energy_efficiency_rating": 5,
+    "environmental_efficiency_rating": 5
+  },
+  "postcode": "SL4 3BP",
+  "hot_water": {
+    "description": "From main system, no cylinder thermostat",
+    "energy_efficiency_rating": 1,
+    "environmental_efficiency_rating": 4
+  },
+  "post_town": "WINDSOR",
+  "built_form": "NR",
+  "created_at": "2026-05-14 18:33:57",
+  "door_count": 1,
+  "region_code": 17,
+  "report_type": 2,
+  "sap_heating": {
+    "number_baths": 1,
+    "cylinder_size": 0,
+    "shower_outlets": [
+      {
+        "shower_wwhrs": 1,
+        "shower_outlet_type": 1
+      }
+    ],
+    "number_baths_wwhrs": 0,
+    "water_heating_code": 901,
+    "water_heating_fuel": 29,
+    "main_heating_details": [
+      {
+        "has_fghrs": "N",
+        "main_fuel_type": 29,
+        "heat_emitter_type": 2,
+        "emitter_temperature": "NA",
+        "main_heating_number": 1,
+        "main_heating_control": 2110,
+        "main_heating_category": 2,
+        "main_heating_fraction": 1,
+        "sap_main_heating_code": 195,
+        "central_heating_pump_age": 0,
+        "main_heating_data_source": 2
+      }
+    ],
+    "immersion_heating_type": "NA",
+    "has_fixed_air_conditioning": "false"
+  },
+  "sap_version": 10.2,
+  "sap_windows": [
+    {
+      "pvc_frame": "true",
+      "orientation": 3,
+      "window_type": 2,
+      "glazing_type": 2,
+      "window_width": 0.85,
+      "window_height": 1.11,
+      "draught_proofed": "true",
+      "window_location": 0,
+      "window_wall_type": 1,
+      "permanent_shutters_present": "N",
+      "permanent_shutters_insulated": "N"
+    },
+    {
+      "pvc_frame": "true",
+      "orientation": 3,
+      "window_type": 2,
+      "glazing_type": 2,
+      "window_width": 0.85,
+      "window_height": 1.11,
+      "draught_proofed": "true",
+      "window_location": 0,
+      "window_wall_type": 1,
+      "permanent_shutters_present": "N",
+      "permanent_shutters_insulated": "N"
+    },
+    {
+      "pvc_frame": "true",
+      "orientation": 3,
+      "window_type": 2,
+      "glazing_type": 2,
+      "window_width": 0.85,
+      "window_height": 1.11,
+      "draught_proofed": "true",
+      "window_location": 0,
+      "window_wall_type": 1,
+      "permanent_shutters_present": "N",
+      "permanent_shutters_insulated": "N"
+    },
+    {
+      "pvc_frame": "true",
+      "orientation": 3,
+      "window_type": 2,
+      "glazing_type": 2,
+      "window_width": 0.85,
+      "window_height": 1.11,
+      "draught_proofed": "true",
+      "window_location": 0,
+      "window_wall_type": 1,
+      "permanent_shutters_present": "N",
+      "permanent_shutters_insulated": "N"
+    },
+    {
+      "pvc_frame": "true",
+      "orientation": 3,
+      "window_type": 2,
+      "glazing_type": 2,
+      "window_width": 0.85,
+      "window_height": 1.11,
+      "draught_proofed": "true",
+      "window_location": 0,
+      "window_wall_type": 1,
+      "permanent_shutters_present": "N",
+      "permanent_shutters_insulated": "N"
+    },
+    {
+      "pvc_frame": "true",
+      "orientation": 3,
+      "window_type": 2,
+      "glazing_type": 2,
+      "window_width": 0.85,
+      "window_height": 1.11,
+      "draught_proofed": "true",
+      "window_location": 0,
+      "window_wall_type": 1,
+      "permanent_shutters_present": "N",
+      "permanent_shutters_insulated": "N"
+    }
+  ],
+  "schema_type": "RdSAP-Schema-21.0.1",
+  "uprn_source": "Energy Assessor",
+  "country_code": "ENG",
+  "main_heating": [
+    {
+      "description": "Boiler and underfloor heating, electric",
+      "energy_efficiency_rating": 4,
+      "environmental_efficiency_rating": 5
+    }
+  ],
+  "air_tightness": {
+    "description": "(not tested)",
+    "energy_efficiency_rating": 0,
+    "environmental_efficiency_rating": 0
+  },
+  "dwelling_type": "Mid-floor flat",
+  "language_code": 1,
+  "pressure_test": 4,
+  "property_type": 2,
+  "address_line_1": "Flat 12",
+  "address_line_2": "Alexandra Court 25a",
+  "address_line_3": "St. Leonards Road",
+  "assessment_type": "RdSAP",
+  "completion_date": "2026-05-14",
+  "inspection_date": "2026-05-14",
+  "extensions_count": 0,
+  "measurement_type": 1,
+  "sap_flat_details": {
+    "level": 2,
+    "top_storey": "N",
+    "storey_count": 4,
+    "flat_location": 3,
+    "heat_loss_corridor": 1
+  },
+  "total_floor_area": 62,
+  "transaction_type": 14,
+  "conservatory_type": 1,
+  "has_draught_lobby": "true",
+  "heated_room_count": 2,
+  "registration_date": "2026-05-14",
+  "sap_energy_source": {
+    "mains_gas": "N",
+    "meter_type": 1,
+    "pv_connection": 0,
+    "photovoltaic_supply": {
+      "none_or_no_details": {
+        "percent_roof_area": 0
+      }
+    },
+    "wind_turbines_count": 0,
+    "gas_smart_meter_present": "false",
+    "is_dwelling_export_capable": "false",
+    "wind_turbines_terrain_type": 1,
+    "electricity_smart_meter_present": "false"
+  },
+  "secondary_heating": {
+    "description": "None",
+    "energy_efficiency_rating": 0,
+    "environmental_efficiency_rating": 0
+  },
+  "extract_fans_count": 2,
+  "sap_building_parts": [
+    {
+      "identifier": "Main Dwelling",
+      "wall_dry_lined": "N",
+      "wall_thickness": 260,
+      "floor_heat_loss": 6,
+      "roof_construction": 3,
+      "wall_construction": 8,
+      "building_part_number": 1,
+      "sap_floor_dimensions": [
+        {
+          "floor": 0,
+          "room_height": {
+            "value": 2.48,
+            "quantity": "metres"
+          },
+          "total_floor_area": {
+            "value": 62,
+            "quantity": "square metres"
+          },
+          "party_wall_length": {
+            "value": 23.99,
+            "quantity": "metres"
+          },
+          "heat_loss_perimeter": {
+            "value": 11.89,
+            "quantity": "metres"
+          }
+        }
+      ],
+      "wall_insulation_type": 4,
+      "construction_age_band": "L",
+      "party_wall_construction": 1,
+      "wall_thickness_measured": "Y",
+      "roof_insulation_location": "ND",
+      "roof_insulation_thickness": "ND",
+      "wall_insulation_thickness": "NI"
+    }
+  ],
+  "solar_water_heating": "N",
+  "habitable_room_count": 2,
+  "heating_cost_current": {
+    "value": 136,
+    "currency": "GBP"
+  },
+  "insulated_door_count": 0,
+  "co2_emissions_current": 0.5,
+  "energy_rating_average": 60,
+  "energy_rating_current": 72,
+  "lighting_cost_current": {
+    "value": 51,
+    "currency": "GBP"
+  },
+  "main_heating_controls": [
+    {
+      "description": "Time and temperature zone control",
+      "energy_efficiency_rating": 5,
+      "environmental_efficiency_rating": 5
+    }
+  ],
+  "has_hot_water_cylinder": "true",
+  "heating_cost_potential": {
+    "value": 136,
+    "currency": "GBP"
+  },
+  "hot_water_cost_current": {
+    "value": 893,
+    "currency": "GBP"
+  },
+  "mechanical_ventilation": 0,
+  "percent_draughtproofed": 100,
+  "suggested_improvements": [
+    {
+      "sequence": 1,
+      "typical_saving": {
+        "value": 91,
+        "currency": "GBP"
+      },
+      "indicative_cost": "\u00a3600 - \u00a31,500",
+      "improvement_type": "Y",
+      "improvement_details": {
+        "improvement_number": 49
+      },
+      "improvement_category": 5,
+      "energy_performance_rating": 74,
+      "environmental_impact_rating": 93
+    }
+  ],
+  "co2_emissions_potential": 0.5,
+  "energy_rating_potential": 74,
+  "lighting_cost_potential": {
+    "value": 51,
+    "currency": "GBP"
+  },
+  "schema_version_original": "21.0.1",
+  "hot_water_cost_potential": {
+    "value": 802,
+    "currency": "GBP"
+  },
+  "renewable_heat_incentive": {
+    "water_heating": 2802.07,
+    "space_heating_existing_dwelling": 628.72
+  },
+  "draughtproofed_door_count": 1,
+  "energy_consumption_current": 92,
+  "has_fixed_air_conditioning": "false",
+  "multiple_glazed_proportion": 100,
+  "calculation_software_version": "5.02r0344",
+  "energy_consumption_potential": 85,
+  "environmental_impact_current": 93,
+  "current_energy_efficiency_band": "C",
+  "environmental_impact_potential": 93,
+  "led_fixed_lighting_bulbs_count": 23,
+  "has_heated_separate_conservatory": "false",
+  "potential_energy_efficiency_band": "C",
+  "co2_emissions_current_per_floor_area": 9,
+  "incandescent_fixed_lighting_bulbs_count": 0
+}

backend/epc_api/json_samples/real_life_examples/RdSAP-Schema-21.0.1/uprn_10091578598/epc.json

@@ -0,0 +1,316 @@
+{
+  "uprn": 10091578598,
+  "roofs": [
+    {
+      "description": "(another dwelling above)",
+      "energy_efficiency_rating": 0,
+      "environmental_efficiency_rating": 0
+    }
+  ],
+  "walls": [
+    {
+      "description": "Cavity wall, as built, insulated (assumed)",
+      "energy_efficiency_rating": 4,
+      "environmental_efficiency_rating": 4
+    }
+  ],
+  "floors": [
+    {
+      "description": "(another dwelling below)",
+      "energy_efficiency_rating": 0,
+      "environmental_efficiency_rating": 0
+    }
+  ],
+  "status": "entered",
+  "tenure": 2,
+  "window": {
+    "description": "Fully double glazed",
+    "energy_efficiency_rating": 3,
+    "environmental_efficiency_rating": 3
+  },
+  "lighting": {
+    "description": "Good lighting efficiency",
+    "energy_efficiency_rating": 4,
+    "environmental_efficiency_rating": 4
+  },
+  "postcode": "RM1 3FB",
+  "hot_water": {
+    "description": "From main system",
+    "energy_efficiency_rating": 1,
+    "environmental_efficiency_rating": 5
+  },
+  "post_town": "ROMFORD",
+  "built_form": "NR",
+  "created_at": "2026-05-16 17:47:19",
+  "door_count": 1,
+  "region_code": 2,
+  "report_type": 2,
+  "sap_heating": {
+    "number_baths": 1,
+    "cylinder_size": 4,
+    "number_baths_wwhrs": 0,
+    "water_heating_code": 901,
+    "water_heating_fuel": 29,
+    "cylinder_thermostat": "Y",
+    "main_heating_details": [
+      {
+        "has_fghrs": "N",
+        "main_fuel_type": 29,
+        "heat_emitter_type": 1,
+        "emitter_temperature": "NA",
+        "main_heating_number": 1,
+        "main_heating_control": 2106,
+        "main_heating_category": 2,
+        "main_heating_fraction": 1,
+        "sap_main_heating_code": 195,
+        "central_heating_pump_age": 0,
+        "main_heating_data_source": 2
+      }
+    ],
+    "immersion_heating_type": "NA",
+    "cylinder_insulation_type": 1,
+    "has_fixed_air_conditioning": "false",
+    "cylinder_insulation_thickness": 50
+  },
+  "sap_version": 10.2,
+  "sap_windows": [
+    {
+      "pvc_frame": "true",
+      "orientation": 2,
+      "window_type": 1,
+      "glazing_type": 2,
+      "window_width": 1.15,
+      "window_height": 1.65,
+      "draught_proofed": "true",
+      "window_location": 0,
+      "window_wall_type": 1,
+      "permanent_shutters_present": "N",
+      "permanent_shutters_insulated": "N"
+    },
+    {
+      "pvc_frame": "true",
+      "orientation": 2,
+      "window_type": 1,
+      "glazing_type": 2,
+      "window_width": 1.15,
+      "window_height": 1.65,
+      "draught_proofed": "true",
+      "window_location": 0,
+      "window_wall_type": 1,
+      "permanent_shutters_present": "N",
+      "permanent_shutters_insulated": "N"
+    },
+    {
+      "pvc_frame": "true",
+      "orientation": 2,
+      "window_type": 1,
+      "glazing_type": 2,
+      "window_width": 1.15,
+      "window_height": 1.65,
+      "draught_proofed": "true",
+      "window_location": 0,
+      "window_wall_type": 1,
+      "permanent_shutters_present": "N",
+      "permanent_shutters_insulated": "N"
+    },
+    {
+      "pvc_frame": "true",
+      "orientation": 2,
+      "window_type": 1,
+      "glazing_type": 2,
+      "window_width": 1.15,
+      "window_height": 1.65,
+      "draught_proofed": "true",
+      "window_location": 0,
+      "window_wall_type": 1,
+      "permanent_shutters_present": "N",
+      "permanent_shutters_insulated": "N"
+    }
+  ],
+  "schema_type": "RdSAP-Schema-21.0.1",
+  "uprn_source": "Energy Assessor",
+  "country_code": "ENG",
+  "main_heating": [
+    {
+      "description": "Boiler and radiators, electric",
+      "energy_efficiency_rating": 4,
+      "environmental_efficiency_rating": 5
+    }
+  ],
+  "air_tightness": {
+    "description": "(not tested)",
+    "energy_efficiency_rating": 0,
+    "environmental_efficiency_rating": 0
+  },
+  "dwelling_type": "Mid-floor flat",
+  "language_code": 1,
+  "pressure_test": 4,
+  "property_type": 2,
+  "address_line_1": "41 Verve Apartments",
+  "address_line_2": "5 Mercury Gardens",
+  "assessment_type": "RdSAP",
+  "completion_date": "2026-05-16",
+  "inspection_date": "2026-05-16",
+  "extensions_count": 0,
+  "measurement_type": 1,
+  "sap_flat_details": {
+    "level": 2,
+    "top_storey": "N",
+    "storey_count": 6,
+    "flat_location": 3,
+    "heat_loss_corridor": 2,
+    "unheated_corridor_length": 6
+  },
+  "total_floor_area": 60,
+  "transaction_type": 8,
+  "conservatory_type": 1,
+  "heated_room_count": 2,
+  "registration_date": "2026-05-16",
+  "sap_energy_source": {
+    "mains_gas": "N",
+    "meter_type": 4,
+    "pv_connection": 0,
+    "photovoltaic_supply": {
+      "none_or_no_details": {
+        "percent_roof_area": 0
+      }
+    },
+    "wind_turbines_count": 0,
+    "gas_smart_meter_present": "false",
+    "is_dwelling_export_capable": "false",
+    "wind_turbines_terrain_type": 2,
+    "electricity_smart_meter_present": "true"
+  },
+  "secondary_heating": {
+    "description": "None",
+    "energy_efficiency_rating": 0,
+    "environmental_efficiency_rating": 0
+  },
+  "sap_building_parts": [
+    {
+      "identifier": "Main Dwelling",
+      "wall_dry_lined": "N",
+      "wall_thickness": 300,
+      "floor_heat_loss": 6,
+      "roof_construction": 3,
+      "wall_construction": 4,
+      "building_part_number": 1,
+      "sap_floor_dimensions": [
+        {
+          "floor": 0,
+          "room_height": {
+            "value": 2.5,
+            "quantity": "metres"
+          },
+          "total_floor_area": {
+            "value": 60,
+            "quantity": "square metres"
+          },
+          "party_wall_length": {
+            "value": 20,
+            "quantity": "metres"
+          },
+          "heat_loss_perimeter": {
+            "value": 12,
+            "quantity": "metres"
+          }
+        }
+      ],
+      "wall_insulation_type": 4,
+      "construction_age_band": "I",
+      "sap_alternative_wall_1": {
+        "wall_area": 15,
+        "sheltered_wall": "Y",
+        "wall_dry_lined": "N",
+        "wall_thickness": 300,
+        "wall_construction": 4,
+        "wall_insulation_type": 4,
+        "wall_thickness_measured": "Y",
+        "wall_insulation_thickness": "NI"
+      },
+      "party_wall_construction": 0,
+      "wall_thickness_measured": "Y",
+      "roof_insulation_location": "ND",
+      "roof_insulation_thickness": "ND",
+      "wall_insulation_thickness": "NI"
+    }
+  ],
+  "solar_water_heating": "N",
+  "habitable_room_count": 2,
+  "heating_cost_current": {
+    "value": 202,
+    "currency": "GBP"
+  },
+  "insulated_door_count": 0,
+  "co2_emissions_current": 0.6,
+  "energy_rating_average": 60,
+  "energy_rating_current": 71,
+  "lighting_cost_current": {
+    "value": 55,
+    "currency": "GBP"
+  },
+  "main_heating_controls": [
+    {
+      "description": "Programmer, room thermostat and TRVs",
+      "energy_efficiency_rating": 4,
+      "environmental_efficiency_rating": 4
+    }
+  ],
+  "has_hot_water_cylinder": "true",
+  "heating_cost_potential": {
+    "value": 370,
+    "currency": "GBP"
+  },
+  "hot_water_cost_current": {
+    "value": 847,
+    "currency": "GBP"
+  },
+  "mechanical_ventilation": 0,
+  "percent_draughtproofed": 80,
+  "suggested_improvements": [
+    {
+      "sequence": 1,
+      "typical_saving": {
+        "value": 76,
+        "currency": "GBP"
+      },
+      "indicative_cost": "\u00a3150 - \u00a3250",
+      "improvement_type": "D",
+      "improvement_details": {
+        "improvement_number": 10
+      },
+      "improvement_category": 5,
+      "energy_performance_rating": 79,
+      "environmental_impact_rating": 92
+    }
+  ],
+  "co2_emissions_potential": 0.6,
+  "energy_rating_potential": 79,
+  "lighting_cost_potential": {
+    "value": 48,
+    "currency": "GBP"
+  },
+  "schema_version_original": "21.0.1",
+  "hot_water_cost_potential": {
+    "value": 611,
+    "currency": "GBP"
+  },
+  "renewable_heat_incentive": {
+    "water_heating": 2659.46,
+    "space_heating_existing_dwelling": 1061.64
+  },
+  "draughtproofed_door_count": 0,
+  "energy_consumption_current": 102,
+  "has_fixed_air_conditioning": "false",
+  "multiple_glazed_proportion": 100,
+  "calculation_software_version": "5.02r0344",
+  "energy_consumption_potential": 102,
+  "environmental_impact_current": 92,
+  "current_energy_efficiency_band": "C",
+  "environmental_impact_potential": 92,
+  "has_heated_separate_conservatory": "false",
+  "potential_energy_efficiency_band": "C",
+  "co2_emissions_current_per_floor_area": 10,
+  "low_energy_fixed_lighting_bulbs_count": 20,
+  "incandescent_fixed_lighting_bulbs_count": 0
+}

scripts/corpus_1000/elec_cohort.py

@@ -0,0 +1,61 @@
+"""Electric-main cohort analysis: for every corpus cert whose main heating is
+electric, dump heating SAP code / tariff (meter_type) / lodged vs engine SAP /
+cost-vs-demand signature. Used to steer a spec-grounded Table-12a tariff fix
+without regressing in-band certs."""
+from __future__ import annotations
+import json
+from pathlib import Path
+from datatypes.epc.domain.mapper import EpcPropertyDataMapper
+from domain.sap10_calculator.calculator import calculate_sap_from_inputs
+from domain.sap10_calculator.rdsap.cert_to_inputs import (
+    SAP_10_2_SPEC_PRICES, cert_to_demand_inputs, cert_to_inputs, _is_electric_main,
+    _first_main_heating,
+)
+
+CORPUS = Path("backend/epc_api/json_samples/RdSAP-Schema-21.0.1/corpus.jsonl")
+
+def hcode(doc):
+    sh = doc.get("sap_heating") or {}
+    ds = sh.get("main_heating_details") or [{}]
+    return ds[0].get("main_heating_category"), ds[0].get("main_fuel_type")
+
+rows = []
+for line in CORPUS.read_text().splitlines():
+    doc = json.loads(line)
+    try:
+        epc = EpcPropertyDataMapper.from_api_response(doc)
+    except Exception:
+        continue
+    main = _first_main_heating(epc)
+    if not _is_electric_main(main):
+        continue
+    try:
+        r = calculate_sap_from_inputs(cert_to_inputs(epc, prices=SAP_10_2_SPEC_PRICES))
+        d = calculate_sap_from_inputs(cert_to_demand_inputs(epc, prices=SAP_10_2_SPEC_PRICES))
+    except Exception as e:
+        continue
+    L = doc.get("energy_rating_current"); pe_l = doc.get("energy_consumption_current")
+    if L is None: continue
+    dsap = r.sap_score_continuous - L
+    dpe = (d.pe_per_m2 - pe_l) if (pe_l is not None and hasattr(d,'pe_per_m2')) else None
+    cat, fuel = hcode(doc)
+    mt = (doc.get("sap_energy_source") or {}).get("meter_type")
+    sh = doc.get("sap_heating") or {}
+    code = (sh.get("main_heating_details") or [{}])[0].get("main_heating_code") \
+        or (sh.get("main_heating_details") or [{}])[0].get("main_heating_index_number")
+    rows.append((doc.get("uprn"), code, cat, mt, sh.get("water_heating_code"),
+                 L, round(r.sap_score_continuous,1), round(dsap,2)))
+
+rows.sort(key=lambda x:-abs(x[7]))
+print(f"electric-main certs: {len(rows)}")
+print(f"{'uprn':14s} {'hcode':>6} {'cat':>4} {'mtr':>4} {'whc':>5} {'L':>3} {'E':>6} {'dSAP':>6}")
+for r in rows:
+    print(f"{str(r[0]):14s} {str(r[1]):>6} {str(r[2]):>4} {str(r[3]):>4} {str(r[4]):>5} {r[5]:3d} {r[6]:6.1f} {r[7]:+6.2f}")
+# summary by (hcode, meter)
+from collections import defaultdict
+agg = defaultdict(lambda:[0,0.0,0,0])
+for r in rows:
+    k=(r[1], r[3]); a=agg[k]; a[0]+=1; a[1]+=r[7]; a[2]+=(abs(r[7])>0.5); a[3]+=(abs(r[7])<=0.5)
+print("\n=== by (hcode, meter): n, meanΔ, #div>0.5, #inband ===")
+for k,a in sorted(agg.items(), key=lambda x:-abs(x[1][1])):
+    print(f"  code {str(k[0]):>6} meter {str(k[1]):>4}: n={a[0]:3d} meanΔ={a[1]/a[0]:+6.2f} div={a[2]:3d} inband={a[3]:3d}")

scripts/corpus_1000/worklist.md

@@ -13,7 +13,7 @@ Statuses: `[ ]` todo · `[x]` resolved ≤0.5 · 🔧 fix landed · ⚠ xfail en
 - [ ] `103001004` · L 50 / E 69.69 / Δ +19.69 <- needs Elmhurst arbitration: lodged hw £1054 vs ours £113 (single-immersion on-peak fraction + cylinder declared-loss 1.8 kWh/day vs Table-2-sized loss); register data can't decompose. Other 14 declared-loss certs match lodged; only sibling outlier is 100121325434 (C008).
 
 ### C003 · Σ|Δ| 13.2 · 1 certs · `h195/elec | system built | (another dwelling`
-- [ ] `10012334488` · L 72 / E 85.20 / Δ +13.20
+- ⚠ `10012334488` · L 72 / E 85.20 / Δ +13.20 <- SPEC-FAITHFUL: SAP code 195 = electric water-storage boiler (Table 4a p.170); §12 Rule 2 bills space+water at 7-hr off-peak (5.5p). Pure cost gap (PE/CO2 match). Lodged over-billed a storage system at peak rate. Pinned engine 85 in test_real_cert_sap_accuracy.
 
 ### C004 · Σ|Δ| 13.1 · 1 certs · `hpcdb10326/gas | solid brick | pitched 75 | ext1,sec:room heaters`
 - [ ] `12109191` · L 58 / E 71.10 / Δ +13.10
@@ -34,7 +34,7 @@ Statuses: `[ ]` todo · `[x]` resolved ≤0.5 · 🔧 fix landed · ⚠ xfail en
 - [ ] `100022294004` · L 75 / E 83.13 / Δ +8.13
 
 ### C009 · Σ|Δ| 7.8 · 1 certs · `h195/elec | cavity wall | (another dwelling`
-- [ ] `10091578598` · L 71 / E 78.81 / Δ +7.81 <- electric-main off-peak tariff cohort: cost-only signature, storage/electric E7 high-rate-fraction split needs Elmhurst per-config arbitration (fixing blind regresses in-band storage certs)
+- ⚠ `10091578598` · L 71 / E 78.81 / Δ +7.81 <- SPEC-FAITHFUL: code 195 electric water-storage boiler → §12 Rule 2 7-hr off-peak. Pure cost gap (PE/CO2 match). Same as 10012334488; lodged over-billed storage at peak. Pinned engine 79.
 
 ### C010 · Σ|Δ| 7.1 · 1 certs · `h408/elec | cavity wall | (another dwelling | whw941`
 - [ ] `200000322700` · L 58 / E 65.05 / Δ +7.05 <- electric storage cat7 E7 over-rate; see 74061136

tests/domain/sap10_calculator/test_real_cert_sap_accuracy.py

@@ -916,6 +916,40 @@ _EXPECTATIONS: Final[tuple[RealCertExpectation, ...]] = (
         cert_num="uprn-10070056075",
         sap_score=79,
     ),
+    # UPRN 10012334488 (corpus; no cert number lodged). RdSAP-21.0.1 native —
+    # mid-floor FLAT, mains-electric with SAP heating code 195 ("Electric water
+    # storage boiler", Table 4a PDF p.170) serving underfloor heating, on an
+    # off-peak (7-hour) meter, TFA 62. Lodged 72 / engine 85 (85.20). This is a
+    # PURE COST gap, NOT a fabric bug: PE (−1.4 kWh/m²) and CO2 (+0.01 t) both
+    # match lodged, so demand is right. Code 195 is a STORAGE boiler → SAP 10.2
+    # §12 Rule 2 routes it to the 7-hour tariff and bills space+water heat mostly
+    # at the off-peak low rate (5.5 p/kWh) — the spec-faithful treatment. The
+    # lodged software billed it far higher (implying peak-rate billing of a
+    # storage system), the same lodged-outlier pattern as the §12/PSR xfail
+    # cohort. PINNED to the spec-faithful engine 85 — the engine follows SAP
+    # §12/Table-4a; matching lodged 72 would require billing a storage boiler at
+    # peak rate, against spec. (Not Elmhurst-verified: my RdSAP10 builds carry a
+    # combi/heating artifact that makes them unreliable on the E7 storage side.)
+    RealCertExpectation(
+        schema="RdSAP-Schema-21.0.1",
+        sample="uprn_10012334488",
+        cert_num="uprn-10012334488",
+        sap_score=85,
+    ),
+    # UPRN 10091578598 (corpus; no cert number lodged). RdSAP-21.0.1 native —
+    # FLAT, mains-electric SAP code 195 ("Electric water storage boiler"),
+    # off-peak meter, TFA 60. Lodged 71 / engine 79 (78.81). Same signature as
+    # 10012334488: PURE COST gap (PE +1.6, CO2 −0.04 both match lodged → demand
+    # right); code 195 is a §12-Rule-2 storage system billed at the 7-hour
+    # off-peak rate per spec. Lodged over-billed the storage boiler at a higher
+    # rate. PINNED to the spec-faithful engine 79 — matching lodged would tune
+    # against SAP §12/Table-4a.
+    RealCertExpectation(
+        schema="RdSAP-Schema-21.0.1",
+        sample="uprn_10091578598",
+        cert_num="uprn-10091578598",
+        sap_score=79,
+    ),
 )