diff --git a/scripts/add_electricity.py b/scripts/add_electricity.py
index e2f7fb655..594988bdb 100755
--- a/scripts/add_electricity.py
+++ b/scripts/add_electricity.py
@@ -137,7 +137,7 @@ def _add_missing_carriers_from_costs(n, costs, carriers):
     n.import_components_from_dataframe(emissions, "Carrier")
 
 
-def load_costs(tech_costs, costs, max_hours, Nyears=1.0):
+def load_costs(tech_costs, config, max_hours, Nyears=1.0):
     # set all asset costs and other parameters
     costs = pd.read_csv(tech_costs, index_col=[0, 1]).sort_index()
 
@@ -145,7 +145,7 @@ def load_costs(tech_costs, costs, max_hours, Nyears=1.0):
     costs.loc[costs.unit.str.contains("/kW"), "value"] *= 1e3
     costs.unit = costs.unit.str.replace("/kW", "/MW")
 
-    fill_values = costs["fill_values"]
+    fill_values = config["fill_values"]
     costs = costs.value.unstack().fillna(fill_values)
 
     costs["capital_cost"] = (
@@ -168,8 +168,8 @@ def load_costs(tech_costs, costs, max_hours, Nyears=1.0):
     costs.at["CCGT", "co2_emissions"] = costs.at["gas", "co2_emissions"]
 
     costs.at["solar", "capital_cost"] = (
-        costs["rooftop_share"] * costs.at["solar-rooftop", "capital_cost"]
-        + (1 - costs["rooftop_share"]) * costs.at["solar-utility", "capital_cost"]
+        config["rooftop_share"] * costs.at["solar-rooftop", "capital_cost"]
+        + (1 - config["rooftop_share"]) * costs.at["solar-utility", "capital_cost"]
     )
 
     def costs_for_storage(store, link1, link2=None, max_hours=1.0):
@@ -193,7 +193,7 @@ def costs_for_storage(store, link1, link2=None, max_hours=1.0):
     )
 
     for attr in ("marginal_cost", "capital_cost"):
-        overwrites = costs.get(attr)
+        overwrites = config.get(attr)
         if overwrites is not None:
             overwrites = pd.Series(overwrites)
             costs.loc[overwrites.index, attr] = overwrites