diff --git a/scripts/add_existing_baseyear.py b/scripts/add_existing_baseyear.py
index 44c9b20e..eea1b3cf 100644
--- a/scripts/add_existing_baseyear.py
+++ b/scripts/add_existing_baseyear.py
@@ -171,9 +171,7 @@ def add_power_capacities_installed_before_baseyear(n, grouping_years, costs, bas
     phased_out = df_agg[df_agg["DateOut"] < baseyear].index
     df_agg.drop(phased_out, inplace=True)
 
-    # calculate remaining lifetime before phase-out (+1 because assuming
-    # phase out date at the end of the year)
-    df_agg["lifetime"] = df_agg.DateOut - df_agg.DateIn + 1
+
 
     # assign clustered bus
     busmap_s = pd.read_csv(snakemake.input.busmap_s, index_col=0).squeeze()
@@ -195,6 +193,10 @@ def add_power_capacities_installed_before_baseyear(n, grouping_years, costs, bas
         grouping_years, np.digitize(df_agg.DateIn, grouping_years, right=True)
     )
 
+    # calculate (adjusted) remaining lifetime before phase-out (+1 because assuming
+    # phase out date at the end of the year)
+    df_agg["lifetime"] = df_agg.DateOut - df_agg["grouping_year"]  + 1
+
     df = df_agg.pivot_table(
         index=["grouping_year", "Fueltype"],
         columns="cluster_bus",