diff --git a/hub/city_model_structure/energy_systems/emission_system.py b/hub/city_model_structure/energy_systems/emission_system.py
index 32bf7c17..e8773013 100644
--- a/hub/city_model_structure/energy_systems/emission_system.py
+++ b/hub/city_model_structure/energy_systems/emission_system.py
@@ -13,7 +13,7 @@ class EmissionSystem:
   def __init__(self):
     self._model_name = None
     self._type = None
-    self._parasitic_energy_consumption = None
+    self._parasitic_energy_consumption = 0
 
   @property
   def model_name(self):