diff --git a/domain/epc/main_heating_system_type.py b/domain/epc/main_heating_system_type.py
index ff3c4233..bea14e6a 100644
--- a/domain/epc/main_heating_system_type.py
+++ b/domain/epc/main_heating_system_type.py
@@ -19,6 +19,9 @@ class MainHeatingSystemType(Enum):
     GAS_COMBI = "Gas boiler, combi"
     GAS_REGULAR = "Gas boiler, regular"
     GAS_CPSU = "Gas CPSU"
+    ELECTRIC_STORAGE_OLD = "Electric storage heaters, old"
+    ELECTRIC_STORAGE_SLIMLINE = "Electric storage heaters, slimline"
+    ELECTRIC_STORAGE_CONVECTOR = "Electric storage heaters, convector"
     ELECTRIC_STORAGE_FAN = "Electric storage heaters, fan"
     DIRECT_ELECTRIC = "Direct-acting electric"
     UNKNOWN = "Unknown"
diff --git a/domain/epc/property_overlays/main_heating_system_overlay.py b/domain/epc/property_overlays/main_heating_system_overlay.py
index 5d61cb5a..1f06eabc 100644
--- a/domain/epc/property_overlays/main_heating_system_overlay.py
+++ b/domain/epc/property_overlays/main_heating_system_overlay.py
@@ -29,6 +29,9 @@ _MAIN_HEATING_CODES: dict[str, int] = {
     "Gas boiler, combi": 104,
     "Gas boiler, regular": 102,
     "Gas CPSU": 120,
+    "Electric storage heaters, old": 401,
+    "Electric storage heaters, slimline": 402,
+    "Electric storage heaters, convector": 403,
     "Electric storage heaters, fan": 404,
     "Direct-acting electric": 191,
 }