diff --git a/domain/sap10_calculator/rdsap/cert_to_inputs.py b/domain/sap10_calculator/rdsap/cert_to_inputs.py
index a873e5f9..bd33cecc 100644
--- a/domain/sap10_calculator/rdsap/cert_to_inputs.py
+++ b/domain/sap10_calculator/rdsap/cert_to_inputs.py
@@ -3282,8 +3282,8 @@ def cert_to_inputs(
             main, epc.sap_energy_source.meter_type, prices
         ),
         hot_water_fuel_cost_gbp_per_kwh=_hot_water_fuel_cost_gbp_per_kwh(
-            epc.sap_heating.water_heating_fuel,
-            main,
+            _water_heating_fuel_code(epc),
+            _water_heating_main(epc),
             epc.sap_energy_source.meter_type,
             prices,
         ),