diff --git a/datatypes/epc/domain/mapper.py b/datatypes/epc/domain/mapper.py
index b3bfdb370..266fa6e71 100644
--- a/datatypes/epc/domain/mapper.py
+++ b/datatypes/epc/domain/mapper.py
@@ -6028,7 +6028,7 @@ def _map_sap_heating(
             MainHeatingDetail(
                 has_fghrs=main.flue_gas_heat_recovery_system,
                 main_fuel_type=_pashub_main_fuel_code(fuel_type),
-                heat_emitter_type=main.emitter,
+                heat_emitter_type=_pashub_heat_emitter_code(main.emitter),
                 emitter_temperature=main.emitter_temperature,
                 fan_flue_present=main.fan_assist,
                 main_heating_control=main.controls,
@@ -7081,6 +7081,20 @@ def _pashub_main_fuel_code(fuel_label: str) -> Union[int, str]:
     return code
 
 
+def _pashub_heat_emitter_code(emitter_label: str) -> Union[int, str]:
+    """Resolve a PasHub surveyed main-heating emitter label to its SAP10 emitter
+    code at the mapper boundary (ADR-0015), reusing the Elmhurst emitter map
+    (`Radiators -> 1`). A blank label passes through unchanged; a non-empty label
+    the map does not cover strict-raises `UnmappedPasHubLabel` here rather than
+    resurfacing downstream as the calculator's `UnmappedSapCode: heat_emitter_type`."""
+    if not emitter_label:
+        return emitter_label
+    code = _ELMHURST_HEAT_EMITTER_TO_SAP10.get(emitter_label)
+    if code is None:
+        raise UnmappedPasHubLabel("heat emitter", emitter_label)
+    return code
+
+
 def _resolve_elmhurst_underfloor_subtype(
     main_floor: ElmhurstFloorDetails,
     main_age_band: str,