diff --git a/domain/epc/property_overlays/main_heating_system_overlay.py b/domain/epc/property_overlays/main_heating_system_overlay.py
index 62be5488a..e15aeeb3c 100644
--- a/domain/epc/property_overlays/main_heating_system_overlay.py
+++ b/domain/epc/property_overlays/main_heating_system_overlay.py
@@ -112,6 +112,10 @@ _CATEGORY_10_ROOM_HEATER_CODES = (
 _ELECTRICITY_FUEL = 29
 _HOUSE_COAL_FUEL = 33
 _ELECTRIC_ROOM_HEATER_CODES = frozenset(range(691, 702))
+# Direct-acting electric boiler (SAP Table 4a 191) — unambiguously electric, so it
+# drags electricity like the electric room heaters (ADR-0045, closing the prior
+# no-fuel gap on 191).
+_ELECTRIC_BOILER_CODE = 191
 
 # Heat pumps (SAP Table 4a 211-224 wet, 521-527 warm-air) are category 4 and
 # unambiguously electric (natural fuel 29). Modellable on the default code's SPF
@@ -173,6 +177,10 @@ _MAIN_HEATING_CODES: dict[str, int] = {
     # generic manual-storage default (ADR-0044).
     "Electric storage heaters, high heat retention": 409,
     "Direct-acting electric": 191,
+    # A-rated electric boiler off the Gas CPSU dumping ground — SAP Table 4a 191
+    # (direct-acting electric boiler). Unambiguously electric, so it drags
+    # electricity below (ADR-0045).
+    "Electric boiler": 191,
     "Electric room heaters": 691,
     "Solid fuel room heater, closed": 633,
     # Solid-fuel room heaters off the Gas CPSU dumping ground (ADR-0045). SAP
@@ -252,6 +260,7 @@ def _natural_fuel_for(code: int) -> Optional[int]:
         code in _ELECTRIC_ROOM_HEATER_CODES
         or code in _HEAT_PUMP_CODES
         or code == _HHR_STORAGE_CODE
+        or code == _ELECTRIC_BOILER_CODE
     ):
         return _ELECTRICITY_FUEL
     if code in _SOLID_FUEL_ROOM_HEATER_CODES:
diff --git a/domain/epc/property_overrides/main_heating_system_type.py b/domain/epc/property_overrides/main_heating_system_type.py
index 2ce796bc8..aaa917df1 100644
--- a/domain/epc/property_overrides/main_heating_system_type.py
+++ b/domain/epc/property_overrides/main_heating_system_type.py
@@ -27,6 +27,7 @@ class MainHeatingSystemType(Enum):
         "Electric storage heaters, high heat retention"
     )
     DIRECT_ELECTRIC = "Direct-acting electric"
+    ELECTRIC_BOILER = "Electric boiler"
     ELECTRIC_ROOM_HEATERS = "Electric room heaters"
     SOLID_FUEL_ROOM_HEATER_CLOSED = "Solid fuel room heater, closed"
     SOLID_FUEL_ROOM_HEATER_OPEN_FIRE = "Solid fuel room heater, open fire"