From 6b64104dc50e1a62b142a6ede602d36cde11b756 Mon Sep 17 00:00:00 2001
From: Khalim Conn-Kowlessar <kconnkowlessar@gmail.com>
Date: Thu, 9 Jul 2026 12:54:46 +0000
Subject: [PATCH] =?UTF-8?q?An=20Energy-Savings=20scenario=20prices=20packa?=
 =?UTF-8?q?ges=20at=20the=20live=20fuel=20rates=20=F0=9F=9F=A5?=
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Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
---
 harness/console.py                            |  4 +-
 .../test_modelling_goal_objectives.py         | 53 +++++++++++++++++++
 2 files changed, 56 insertions(+), 1 deletion(-)

diff --git a/harness/console.py b/harness/console.py
index a9aa222b5..06c16d81e 100644
--- a/harness/console.py
+++ b/harness/console.py
@@ -39,6 +39,7 @@ from orchestration.modelling_orchestrator import (
     _candidate_recommendations,  # pyright: ignore[reportPrivateUsage]
 )
 from orchestration.property_baseline_orchestrator import PropertyBaselineOrchestrator
+from repositories.fuel_rates.fuel_rates_repository import FuelRatesRepository
 from repositories.fuel_rates.fuel_rates_static_file_repository import (
     FuelRatesStaticFileRepository,
 )
@@ -182,6 +183,7 @@ def run_modelling(
     considered_measures: Optional[frozenset[MeasureType]] = None,
     products: Optional[ProductRepository] = None,
     scenario: Optional[Scenario] = None,
+    fuel_rates: Optional[FuelRatesRepository] = None,
     print_table: bool = True,
 ) -> Plan:
     """Run ONLY the Modelling stage over ``epc`` with no database — skipping
@@ -240,7 +242,7 @@ def run_modelling(
     ModellingOrchestrator(
         unit_of_work=lambda: unit,
         calculator=Sap10Calculator(),
-        fuel_rates=FuelRatesStaticFileRepository(),
+        fuel_rates=fuel_rates or FuelRatesStaticFileRepository(),
     ).run(
         property_ids=[_PROPERTY_ID],
         scenario_ids=[scenario_id],
diff --git a/tests/orchestration/test_modelling_goal_objectives.py b/tests/orchestration/test_modelling_goal_objectives.py
index 962c94e24..ac7492085 100644
--- a/tests/orchestration/test_modelling_goal_objectives.py
+++ b/tests/orchestration/test_modelling_goal_objectives.py
@@ -9,11 +9,19 @@ carbon-optimal packages diverge at a £16,000 budget.
 
 from __future__ import annotations
 
+import dataclasses
+
 from datatypes.epc.domain.epc_property_data import EpcPropertyData
+from domain.fuel_rates.fuel import Fuel
+from domain.fuel_rates.fuel_rates import FuelRate, FuelRates
 from domain.modelling.measure_type import MeasureType
 from domain.modelling.plan import Plan
 from domain.modelling.scenario import Scenario
 from harness.console import run_modelling
+from repositories.fuel_rates.fuel_rates_repository import FuelRatesRepository
+from repositories.fuel_rates.fuel_rates_static_file_repository import (
+    FuelRatesStaticFileRepository,
+)
 from tests.domain.modelling._elmhurst_recommendation import (
     parse_recommendation_summary,
 )
@@ -57,3 +65,48 @@ def test_reducing_co2_scenario_buys_carbon_not_sap() -> None:
     )
     selected = {measure.measure_type for measure in carbon_led.measures}
     assert MeasureType.GAS_BOILER_UPGRADE not in selected
+
+
+class _FixedFuelRates(FuelRatesRepository):
+    def __init__(self, rates: FuelRates) -> None:
+        self._rates = rates
+
+    def get_current(self) -> FuelRates:
+        return self._rates
+
+
+def _cheap_electricity_snapshot() -> FuelRates:
+    """The committed snapshot with electricity at 1p/kWh — a world where any
+    electric heating out-bills gas, while SAP's internal price book (which the
+    calculator rates against) is unmoved."""
+    base = FuelRatesStaticFileRepository().get_current()
+    rates = dict(base.rates)
+    rates[Fuel.ELECTRICITY] = FuelRate(
+        unit_rate_p_per_kwh=1.0,
+        standing_charge_p_per_day=rates[Fuel.ELECTRICITY].standing_charge_p_per_day,
+    )
+    return dataclasses.replace(base, rates=rates)
+
+
+def test_energy_savings_scenario_prices_packages_at_the_live_fuel_rates() -> None:
+    # Arrange — SAP is itself a cost metric, but it prices energy from its
+    # internal tariff book. The Energy Savings goal must price at the *live*
+    # Fuel Rates snapshot: with 1p/kWh electricity, electric heating slashes
+    # the bill even though SAP still scores the gas boiler package higher.
+    epc = _solid_brick_dwelling()
+
+    # Act
+    plan: Plan = run_modelling(
+        epc,
+        scenario=_scenario("Energy Savings", budget=16000.0),
+        fuel_rates=_FixedFuelRates(_cheap_electricity_snapshot()),
+        print_table=False,
+    )
+
+    # Assert — the bill objective abandons the boiler for electric heating.
+    selected = {measure.measure_type for measure in plan.measures}
+    assert MeasureType.GAS_BOILER_UPGRADE not in selected
+    assert selected & {
+        MeasureType.AIR_SOURCE_HEAT_PUMP,
+        MeasureType.HIGH_HEAT_RETENTION_STORAGE_HEATERS,
+    }