diff --git a/infrastructure/postgres/epc_property_table.py b/infrastructure/postgres/epc_property_table.py
index d2c2de654..512621d6c 100644
--- a/infrastructure/postgres/epc_property_table.py
+++ b/infrastructure/postgres/epc_property_table.py
@@ -168,6 +168,9 @@ class EpcPropertyModel(SQLModel, table=True):
     )
     heating_cylinder_insulation_thickness_mm: Optional[int] = Field(default=None)
     heating_cylinder_volume_measured_l: Optional[int] = Field(default=None)
+    # #1665: read by cert_to_inputs (§4 cylinder loss); dropping it billed the
+    # cylinder at the Table 2b age-band default (worst case -15.53 SAP).
+    heating_cylinder_heat_loss: Optional[float] = Field(default=None)
     heating_wwhrs_index_number_1: Optional[int] = Field(default=None)
     heating_wwhrs_index_number_2: Optional[int] = Field(default=None)
     heating_shower_outlet_type: Optional[Union[int, str]] = Field(
@@ -359,6 +362,7 @@ class EpcPropertyModel(SQLModel, table=True):
             heating_secondary_heating_type=h.secondary_heating_type,
             heating_cylinder_insulation_thickness_mm=h.cylinder_insulation_thickness_mm,
             heating_cylinder_volume_measured_l=h.cylinder_volume_measured_l,
+            heating_cylinder_heat_loss=h.cylinder_heat_loss,
             heating_wwhrs_index_number_1=h.instantaneous_wwhrs.wwhrs_index_number1,
             heating_wwhrs_index_number_2=h.instantaneous_wwhrs.wwhrs_index_number2,
             heating_shower_outlet_type=shower.shower_outlet_type if shower else None,
diff --git a/repositories/epc/epc_postgres_repository.py b/repositories/epc/epc_postgres_repository.py
index caa038e4e..81620b069 100644
--- a/repositories/epc/epc_postgres_repository.py
+++ b/repositories/epc/epc_postgres_repository.py
@@ -909,6 +909,7 @@ class EpcPostgresRepository(EpcRepository):
             secondary_heating_type=p.heating_secondary_heating_type,
             cylinder_insulation_thickness_mm=p.heating_cylinder_insulation_thickness_mm,
             cylinder_volume_measured_l=p.heating_cylinder_volume_measured_l,
+            cylinder_heat_loss=p.heating_cylinder_heat_loss,
             number_baths=p.heating_number_baths,
             number_baths_wwhrs=p.heating_number_baths_wwhrs,
             electric_shower_count=p.heating_electric_shower_count,
diff --git a/tests/repositories/epc/test_epc_persistence_field_coverage.py b/tests/repositories/epc/test_epc_persistence_field_coverage.py
index a3f12bb12..af416983a 100644
--- a/tests/repositories/epc/test_epc_persistence_field_coverage.py
+++ b/tests/repositories/epc/test_epc_persistence_field_coverage.py
@@ -60,7 +60,6 @@ _UNPERSISTED_ALLOWLIST: dict[str, str] = {
     "SapRoomInRoofSurface": "FE child table pending — room-in-roof surface detail",
     # --- Nested gaps the calculator does NOT read (dormant); no FE column.
     "SapAlternativeWall.is_basement": "dormant — not read by the calculator; no FE column",
-    "SapHeating.cylinder_heat_loss": "dormant — not read by the calculator; no FE column",
     # --- DELIBERATELY not persisted (#1656). These four ARE read by the
     # calculator (`heat_transmission.py:994` wall U, `:1068` roof U, `:1118`
     # floor U, `:955` basement wall) — do NOT re-label them "not read by the