diff --git a/hub/city_model_structure/building.py b/hub/city_model_structure/building.py
index e0b18c66..cbbda322 100644
--- a/hub/city_model_structure/building.py
+++ b/hub/city_model_structure/building.py
@@ -759,14 +759,14 @@ class Building(CityObject):
         if demand_type.lower() == consumption_type.lower():
           if consumption_type in (cte.HEATING, cte.DOMESTIC_HOT_WATER):
             for generation_system in energy_system_generation_systems:
-              coefficient_of_performance = generation_system.generic_generation_system.heat_efficiency
+              coefficient_of_performance = generation_system.generic_generation_system[0].heat_efficiency
           elif consumption_type == cte.COOLING:
             for generation_system in energy_system_generation_systems:
-              coefficient_of_performance = generation_system.generic_generation_system.cooling_efficiency
+              coefficient_of_performance = generation_system.generic_generation_system[0].cooling_efficiency
           elif consumption_type == cte.ELECTRICITY:
             for generation_system in energy_system_generation_systems:
               coefficient_of_performance = \
-                generation_system.generic_generation_system.electricity_efficiency
+                generation_system.generic_generation_system[0].electricity_efficiency
     if coefficient_of_performance == 0:
       values = [0] * len(demand)
       final_energy_consumed = values
@@ -799,8 +799,8 @@ class Building(CityObject):
     for energy_system in self.energy_systems:
       energy_system_generation_systems = energy_system.generation_systems
       for generation_system in energy_system_generation_systems:
-        if generation_system.generic_generation_system.type == cte.PHOTOVOLTAIC:
-          _efficiency = generation_system.generic_generation_system.electricity_efficiency
+        if generation_system.generic_generation_system[0].type == cte.PHOTOVOLTAIC:
+          _efficiency = generation_system.generic_generation_system[0].electricity_efficiency
           self._onsite_electrical_production = {}
           for _key in self.roofs[0].global_irradiance.keys():
             _results = [0 for _ in range(0, len(self.roofs[0].global_irradiance[_key]))]
diff --git a/tests/test_systems_factory.py b/tests/test_systems_factory.py
index f502cf8b..f2e3a7b4 100644
--- a/tests/test_systems_factory.py
+++ b/tests/test_systems_factory.py
@@ -183,6 +183,10 @@ class TestSystemsFactory(TestCase):
       building.energy_systems = _building_energy_systems
 
     for building in self._city.buildings:
+      print(building.heating_consumption[cte.YEAR][0])
+      print(building.cooling_consumption[cte.YEAR][0])
+      print(building.domestic_hot_water_consumption[cte.YEAR][0])
+      print(building.onsite_electrical_production[cte.YEAR][0])
       self.assertLess(0, building.heating_consumption[cte.YEAR][0])
       self.assertLess(0, building.cooling_consumption[cte.YEAR][0])
       self.assertLess(0, building.domestic_hot_water_consumption[cte.YEAR][0])