diff --git a/src/akkudoktoreos/class_ems.py b/src/akkudoktoreos/class_ems.py
index 6dd75f1..f20443a 100644
--- a/src/akkudoktoreos/class_ems.py
+++ b/src/akkudoktoreos/class_ems.py
@@ -4,24 +4,6 @@
 import numpy as np
 
 
-def replace_nan_with_none(
-    data: Union[np.ndarray, dict, list, float],
-) -> Union[List, dict, float, None]:
-    if data is None:
-        return None
-    if isinstance(data, np.ndarray):
-        # Use numpy vectorized approach
-        return np.where(np.isnan(data), None, data).tolist()
-    elif isinstance(data, dict):
-        return {key: replace_nan_with_none(value) for key, value in data.items()}
-    elif isinstance(data, list):
-        return [replace_nan_with_none(element) for element in data]
-    elif isinstance(data, (float, np.floating)) and np.isnan(data):
-        return None
-    else:
-        return data
-
-
 class EnergieManagementSystem:
     def __init__(
         self,
@@ -156,4 +138,22 @@ def simuliere(self, start_stunde: int) -> dict:
             "Haushaltsgeraet_wh_pro_stunde": haushaltsgeraet_wh_pro_stunde,
         }
 
-        return replace_nan_with_none(out)
+        # List output keys where the first element needs to be changed to None
+        keys_to_modify = [
+            "Last_Wh_pro_Stunde",
+            "Netzeinspeisung_Wh_pro_Stunde",
+            "Netzbezug_Wh_pro_Stunde",
+        ]
+
+        # Loop through each key in the list
+        for key in keys_to_modify:
+            # Convert the NumPy array to a list
+            element_list = out[key].tolist()
+
+            # Change the first value to None
+            element_list[0] = None
+
+            # Assign the modified list back to the dictionary
+            out[key] = element_list
+
+        return out
diff --git a/tests/test_class_ems.py b/tests/test_class_ems.py
index b7979e5..ed24f09 100644
--- a/tests/test_class_ems.py
+++ b/tests/test_class_ems.py
@@ -279,15 +279,15 @@ def test_simulation(create_ems_instance):
 
     # Verify that the value at index 0 is 'None'
     assert (
-        result["Last_Wh_pro_Stunde"][0] == 0.0
+        result["Last_Wh_pro_Stunde"][0] is None
     ), "The value at index 0 of 'Last_Wh_pro_Stunde' should be None."
 
     # Check that 'Netzeinspeisung_Wh_pro_Stunde' and 'Netzbezug_Wh_pro_Stunde' are consistent
     assert (
-        result["Netzeinspeisung_Wh_pro_Stunde"][0] == 0.0
+        result["Netzeinspeisung_Wh_pro_Stunde"][0] is None
     ), "The value at index 0 of 'Netzeinspeisung_Wh_pro_Stunde' should be None."
     assert (
-        result["Netzbezug_Wh_pro_Stunde"][0] == 0.0
+        result["Netzbezug_Wh_pro_Stunde"][0] is None
     ), "The value at index 0 of 'Netzbezug_Wh_pro_Stunde' should be None."
     assert (
         result["Netzbezug_Wh_pro_Stunde"][1] == 21679.13