diff --git a/recommendations/Costs.py b/recommendations/Costs.py
index 5554245f..ee4db7eb 100644
--- a/recommendations/Costs.py
+++ b/recommendations/Costs.py
@@ -758,32 +758,31 @@ class Costs:
         else:
             system_cost = [c for c in INSTALLER_SOLAR_COSTS if c["n_panels"] == n_panels][0]["cost"]
 
-        total_cost = array_cost if array_cost is not None else system_cost
+        subtotal = array_cost if array_cost is not None else system_cost
 
         if has_battery:
             battery_cost = [c for c in INSTALLER_SOLAR_BATTERY_COSTS if c["capacity_kwh"] == battery_kwh][0]["cost"]
-            total_cost += battery_cost
+            subtotal += battery_cost
 
         scaffolding_cost = [c for c in INSTALLER_SCAFFOLDING_COSTS if c["stories"] == n_floors][0]["cost"]
-        total_cost += scaffolding_cost
+        subtotal += scaffolding_cost
 
         if needs_inverter:
-            total_cost += INSTALLER_SOLAR_PV_INVERTER_COST
+            subtotal += INSTALLER_SOLAR_PV_INVERTER_COST
             # We also add an additional labour cost
-            total_cost += INSTALLER_SOLAR_PV_INVERTER_LABOUR_COST
+            subtotal += INSTALLER_SOLAR_PV_INVERTER_LABOUR_COST
 
         # We add an additional cost for scaffolding
-
-        subtotal_before_vat = total_cost / (1 + self.VAT_RATE)
-
-        vat = total_cost - subtotal_before_vat
+        # The costs from installers exclude VAT
+        vat = subtotal * self.VAT_RATE
+        total_cost = subtotal + vat
 
         # Labour hours are based on estimates from online research but an average team seems to consist of 3 people
         # and most jobs take around 2 days. Assuming an 8 hour day for 3 people across 2 days, gives us 48 hours of
         # labour
         return {
             "total": total_cost,
-            "subtotal": subtotal_before_vat,
+            "subtotal": subtotal,
             "vat": vat,
             "labour_hours": 48,
             "labour_days": 2,
@@ -1163,17 +1162,18 @@ class Costs:
             cost = [x for x in INSTALLER_ASHP_COSTS if x][0]["cost"]
 
         # We add some contingency since there are additional costs such as resizing radiators, that could be required
-        total_cost = cost * (1 + self.CONTINGENCY)
-        subtotal_before_vat = total_cost / (1 + self.VAT_RATE)
-        vat = total_cost - subtotal_before_vat
+        subtotal = cost * (1 + self.CONTINGENCY)
+        # The costs from installers exclude VAT
+        vat = subtotal * self.VAT_RATE
+        total_cost = subtotal + vat
 
         # We assume 5 days installation
         labour_days = 5
         labour_hours = labour_days * 8
 
         return {
-            "total": total_cost,
-            "subtotal": subtotal_before_vat,
+            "total": subtotal,
+            "subtotal": subtotal,
             "vat": vat,
             "labour_hours": labour_hours,
             "labour_days": labour_days,