diff --git a/co2_emission/co2_emission.py b/co2_emission/co2_emission.py
index ea781fd..6739ca7 100644
--- a/co2_emission/co2_emission.py
+++ b/co2_emission/co2_emission.py
@@ -39,43 +39,34 @@ class Co2Emission:
     results = {}
     for energy_system in self._building.energy_systems:
       fuel_type = energy_system.generation_system.generic_generation_system.fuel_type
+      emissions_factor = self._emissions_factor[fuel_type]
       for demand_type in energy_system.demand_types:
         if demand_type == cte.ELECTRICITY:
           continue
         results_by_time_period = {}
         if demand_type == cte.HEATING:
           for time_period in self._building.heating_consumption:
-            values = []
-            for value in self._building.heating_consumption[time_period]:
-              values.append(value * self._emissions_factor[fuel_type])
+            values = [v * emissions_factor for v in self._building.heating_consumption[time_period]]
             results_by_time_period[time_period] = values
         if demand_type == cte.COOLING:
           for time_period in self._building.cooling_consumption:
-            values = []
-            for value in self._building.cooling_consumption[time_period]:
-              values.append(value * self._emissions_factor[fuel_type])
+            values = [v * emissions_factor for v in self._building.cooling_consumption[time_period]]
             results_by_time_period[time_period] = values
         if demand_type == cte.DOMESTIC_HOT_WATER:
           for time_period in self._building.domestic_hot_water_consumption:
-            values = []
-            for value in self._building.domestic_hot_water_consumption[time_period]:
-              values.append(value * self._emissions_factor[fuel_type])
+            values = [v * emissions_factor for v in self._building.domestic_hot_water_consumption[time_period]]
             results_by_time_period[time_period] = values
         results[demand_type] = results_by_time_period
-
+    emission_factor = self._emissions_factor[cte.ELECTRICITY]
     results_by_time_period = {}
     for time_period in self._building.lighting_electrical_demand:
-      values = []
-      for value in self._building.lighting_electrical_demand[time_period]:
-        values.append(value * self._emissions_factor[cte.ELECTRICITY])
+      values = [v * emission_factor for v in self._building.lighting_electrical_demand[time_period]]
       results_by_time_period[time_period] = values
     results[cte.LIGHTING] = results_by_time_period
 
     results_by_time_period = {}
     for time_period in self._building.appliances_electrical_demand:
-      values = []
-      for value in self._building.appliances_electrical_demand[time_period]:
-        values.append(value * self._emissions_factor[cte.ELECTRICITY])
+      values = [v * emission_factor for v in self._building.appliances_electrical_demand[time_period]]
       results_by_time_period[time_period] = values
     results[cte.APPLIANCES] = results_by_time_period