diff --git a/process/costs_2015.py b/process/costs_2015.py
index 0b4fa163..2a47dbc2 100644
--- a/process/costs_2015.py
+++ b/process/costs_2015.py
@@ -142,7 +142,7 @@ def run(self, output: bool):
         self.mean_electric_output = (
             heat_transport_variables.pnetelmw * cost_variables.cpfact
         )
-        self.annual_electric_output = self.mean_electric_output * 24.0e0 * 265.25e0
+        self.annual_electric_output = self.mean_electric_output * 24.0e0 * 365.25e0
 
         # Annual maintenance cost.
         self.maintenance = (