diff --git a/recommendations/HeatingRecommender.py b/recommendations/HeatingRecommender.py
index fd2dfe38..ab377369 100644
--- a/recommendations/HeatingRecommender.py
+++ b/recommendations/HeatingRecommender.py
@@ -229,9 +229,11 @@ class HeatingRecommender:
         ashp_recommendations = []
         for controls_rec in controls_recommendations:
 
+            ashp_costs_with_controls = ashp_costs.copy()
+
             if controls_rec:
-                for key in ashp_costs:
-                    ashp_costs[key] += controls_rec[key]
+                for key in ashp_costs_with_controls:
+                    ashp_costs_with_controls[key] += controls_rec[key]
 
             if controls_rec is None:
                 description = "Install an air source heat pump."
@@ -244,13 +246,16 @@ class HeatingRecommender:
             # includes the boiler upgrade scheme and that the cavity and loft need to be treated, to ensure access
             # to the funding
             if has_cavity_or_loft_recommendations:
-                description = description + (f" The cost includes the £"
-                                             f"{BOILER_UPGRADE_SCHEME_ASHP_VALUE} boiler upgrade scheme grant. "
-                                             f"You must ensure that the property has an insulated cavity and "
-                                             f"270mm+ loft insulation to qualify for the grant")
+                description = description + (
+                    f" The cost includes the £"
+                    f"{BOILER_UPGRADE_SCHEME_ASHP_VALUE} boiler upgrade scheme grant. "
+                    f"You must ensure that the property has an insulated cavity and "
+                    f"270mm+ loft insulation to qualify for the grant"
+                )
             else:
-                description = description + (f" The cost includes the £"
-                                             f"{BOILER_UPGRADE_SCHEME_ASHP_VALUE} boiler upgrade scheme grant")
+                description = description + (
+                    f" The cost includes the £{BOILER_UPGRADE_SCHEME_ASHP_VALUE} boiler upgrade scheme grant"
+                )
 
             simulation_config = {
                 "mainheat_energy_eff_ending": "Good",
@@ -321,7 +326,7 @@ class HeatingRecommender:
                 "already_installed": already_installed,
                 "simulation_config": simulation_config,
                 "description_simulation": description_simulation,
-                **ashp_costs
+                **ashp_costs_with_controls
             }
 
             ashp_recommendations.append(ashp_recommendation)