diff --git a/districtgenerator/functions/opti_central.py b/districtgenerator/functions/opti_central.py
index 5881707d..f5e04728 100644
--- a/districtgenerator/functions/opti_central.py
+++ b/districtgenerator/functions/opti_central.py
@@ -1721,7 +1721,8 @@ def helper_func_extract_eh_results(model, results_dict, variable_type, device_se
     # Heat devices
     for n in range(nbuildings):
         for device in ECS_HEAT:
-            results_dict[n][device] = {}
+            if not results_dict[n].get(device):
+                results_dict[n][device] = {}
             results_dict[n][device]["Q_th"] = []
             for t in time_steps:
                 results_dict[n][device]["Q_th"].append(round(pyo.value(model.heat_dom[device, n, t]), 0))
@@ -1729,7 +1730,8 @@ def helper_func_extract_eh_results(model, results_dict, variable_type, device_se
     # Cooling devices
     for n in range(nbuildings):
         for device in ECS_COOL:
-            results_dict[n][device] = {}
+            if not results_dict[n].get(device):
+                results_dict[n][device] = {}
             results_dict[n][device]["Q_cool"] = []
             for t in time_steps:
                 results_dict[n][device]["Q_cool"].append(round(pyo.value(model.cool_dom[device, n, t]), 0))
@@ -1754,7 +1756,8 @@ def helper_func_extract_eh_results(model, results_dict, variable_type, device_se
     # Power devices
     for n in range(nbuildings):
         for device in ECS_POWER:
-            results_dict[n][device] = {}
+            if not results_dict[n].get(device):
+                results_dict[n][device] = {}
             results_dict[n][device]["P_el"] = []
             for t in time_steps:
                 results_dict[n][device]["P_el"].append(round(pyo.value(model.power_dom[device, n, t]), 0))
@@ -1762,7 +1765,8 @@ def helper_func_extract_eh_results(model, results_dict, variable_type, device_se
     # Storage devices
     for n in range(nbuildings):
         for device in ECS_STORAGE:
-            results_dict[n][device] = {}
+            if not results_dict[n].get(device):
+                results_dict[n][device] = {}
             for v in ("ch", "dch", "soc"):
                 results_dict[n][device][v] = []
             for t in time_steps: