diff --git a/backend/app/assumptions.py b/backend/app/assumptions.py
index 5f8cb85c..80baa69f 100644
--- a/backend/app/assumptions.py
+++ b/backend/app/assumptions.py
@@ -1,7 +1,7 @@
 # Assumes that the average efficiency of an air source heat pump is 250%, taking the median of the 200-400% range,
 # which is often quoted as a sensible efficiency range for air source heat pumps.
 PESSIMISTIC_ASHP_EFFICIENCY = 200
-AVERAGE_ASHP_EFFICIENCY = 300
+AVERAGE_ASHP_EFFICIENCY = 250
 
 # Conservative estimate of the proportion of electricity that will be consumed, whereas the rest will
 # be exported
@@ -11,34 +11,36 @@ DESCRIPTIONS_TO_FUEL_TYPES = {
     "Air source heat pump, radiators, electric": {
         "fuel": "Electricity", "cop": AVERAGE_ASHP_EFFICIENCY / 100
     },
-    "Boiler and radiators, mains gas": {"fuel": 'Natural Gas', "cop": 0.9},
+    "Boiler and radiators, mains gas": {"fuel": 'Natural Gas', "cop": 0.85},
     'Electric storage heaters': {"fuel": 'Electricity', "cop": 1},
     "Electric immersion, off-peak": {"fuel": 'Electricity', "cop": 1},
     "Electric storage heaters, radiators": {"fuel": 'Electricity', "cop": 1},
     "Room heaters, electric": {"fuel": 'Electricity', "cop": 1},
     "Electric immersion, standard tariff": {"fuel": 'Electricity', "cop": 1},
     "Portable electric heaters assumed for most rooms": {"fuel": 'Electricity', "cop": 1},
-    "Boiler and radiators, LPG": {"fuel": 'LPG', "cop": 0.9},
+    "Boiler and radiators, LPG": {"fuel": 'LPG', "cop": 0.85},
     "Room heaters, dual fuel (mineral and wood)": {"fuel": 'Wood Logs', "cop": 1},
-    "Room heaters, mains gas": {"fuel": 'Natural Gas', "cop": 0.9},
-    "Warm air, mains gas": {"fuel": 'Natural Gas', "cop": 0.9},
-    "Boiler, mains gas": {"fuel": 'Natural Gas', "cop": 0.9},
-    "Gas multipoint": {"fuel": "Natural Gas", "cop": 0.9},
+    "Room heaters, mains gas": {"fuel": 'Natural Gas', "cop": 0.85},
+    "Warm air, mains gas": {"fuel": 'Natural Gas', "cop": 0.85},
+    "Boiler, mains gas": {"fuel": 'Natural Gas', "cop": 0.85},
+    "Gas multipoint": {"fuel": "Natural Gas", "cop": 0.85},
     "Warm air, Electricaire": {"fuel": "Electricity", "cop": 1},
-    "Gas boiler/circulator": {"fuel": "Natural Gas", "cop": 0.9},
-    "Boiler and underfloor heating, mains gas": {"fuel": "Natural Gas", "cop": 0.9},
+    "Gas boiler/circulator": {"fuel": "Natural Gas", "cop": 0.85},
+    "Boiler and underfloor heating, mains gas": {"fuel": "Natural Gas", "cop": 0.85},
     "No system present: electric heaters assumed": {"fuel": "Electricity", "cop": 1},
     "Electric instantaneous at point of use": {"fuel": "Electricity", "cop": 1},
-    "Boiler and radiators, oil": {"fuel": "Oil", "cop": 0.9},
+    "Boiler and radiators, oil": {"fuel": "Oil", "cop": 0.85},
     "Electric storage heaters, Electric storage heaters": {"fuel": "Electricity", "cop": 1},
-    "Boiler and radiators, electric": {"fuel": "Electricity", "cop": 0.9},
-    "Gas boiler/circulator, no cylinder thermostat": {"fuel": "Natural Gas", "cop": 0.9},
-    "Boiler and radiators, dual fuel (mineral and wood)": {"fuel": "Wood Logs", "cop": 0.9},
+    "Boiler and radiators, electric": {"fuel": "Electricity", "cop": 0.85},
+    "Gas boiler/circulator, no cylinder thermostat": {"fuel": "Natural Gas", "cop": 0.85},
+    "Boiler and radiators, dual fuel (mineral and wood)": {"fuel": "Wood Logs", "cop": 0.85},
     "Electric immersion, standard tariff, plus solar": {"fuel": "Electricity + Solar Thermal", "cop": 1},
-    "From main system, flue gas heat recovery": {"fuel": "Natural Gas", "cop": 0.9},
+    "From main system, flue gas heat recovery": {"fuel": "Natural Gas", "cop": 0.85},
     "Electric underfloor heating": {"fuel": "Electricity", "cop": 1},
     "No system present: electric immersion assumed": {"fuel": "Electricity", "cop": 1},
     "Air source heat pump, underfloor, electric": {
         "fuel": "Electricity", "cop": AVERAGE_ASHP_EFFICIENCY / 100
     },
+    "Gas instantaneous at point of use": {"fuel": "Natural Gas", "cop": 0.85},
+    "Room heaters, wood logs": {"fuel": "Wood Logs", "cop": 1},
 }