diff --git a/scripts/make_summary.py b/scripts/make_summary.py
index 891e443f..8fbe02f1 100644
--- a/scripts/make_summary.py
+++ b/scripts/make_summary.py
@@ -299,9 +299,9 @@ def calculate_energy(n, label, energy):
                 )
                 # remove values where bus is missing (bug in nomopyomo)
                 no_bus = c.df.index[c.df["bus" + port] == ""]
-                totals.loc[no_bus] = n.component_attrs[c.name].loc[
+                totals.loc[no_bus] = float(n.component_attrs[c.name].loc[
                     "p" + port, "default"
-                ]
+                ])
                 c_energies -= totals.groupby(c.df.carrier).sum()
 
         c_energies = pd.concat([c_energies], keys=[c.list_name])