diff --git a/doc/release_notes.rst b/doc/release_notes.rst
index cfb67d77..b7035974 100644
--- a/doc/release_notes.rst
+++ b/doc/release_notes.rst
@@ -44,6 +44,8 @@ Upcoming Release
   network has been moved from ``focus_weights:`` to ``clustering:
   focus_weights:``. Backwards compatibility to old config files is maintained.
 
+* Add VOM as marginal cost to PtX processes.
+
 * The ``mock_snakemake`` function can now be used with a Snakefile from a different directory using the new ``root_dir`` argument.
 
 * Add option to capture CO2 contained in biogas when upgrading (``sector: biogas_to_gas_cc``).
diff --git a/scripts/prepare_sector_network.py b/scripts/prepare_sector_network.py
index aaaf3773..9c1a85d7 100644
--- a/scripts/prepare_sector_network.py
+++ b/scripts/prepare_sector_network.py
@@ -815,6 +815,7 @@ def add_ammonia(n, costs):
         efficiency2=-cf_industry["MWh_H2_per_tNH3_electrolysis"]
         / cf_industry["MWh_elec_per_tNH3_electrolysis"],  # input: MW_H2 per MW_elec
         capital_cost=costs.at["Haber-Bosch", "fixed"] / MWh_elec_per_MWh_NH3,
+        marginal_cost=costs.at["Haber-Bosch", "VOM"] / MWh_elec_per_MWh_NH3,
         lifetime=costs.at["Haber-Bosch", "lifetime"],
     )
 
@@ -1025,7 +1026,7 @@ def insert_gas_distribution_costs(n, costs):
         f"Inserting gas distribution grid with investment cost factor of {f_costs}"
     )
 
-    capital_cost = costs.loc["electricity distribution grid"]["fixed"] * f_costs
+    capital_cost = costs.at["electricity distribution grid", "fixed"] * f_costs
 
     # gas boilers
     gas_b = n.links.index[
@@ -1102,6 +1103,7 @@ def add_storage_and_grids(n, costs):
             efficiency=costs.at["OCGT", "efficiency"],
             capital_cost=costs.at["OCGT", "fixed"]
             * costs.at["OCGT", "efficiency"],  # NB: fixed cost is per MWel
+            marginal_cost=costs.at["OCGT", "VOM"],
             lifetime=costs.at["OCGT", "lifetime"],
         )
 
@@ -2350,7 +2352,7 @@ def add_biomass(n, costs):
             + costs.at["BtL", "CO2 stored"],
             p_nom_extendable=True,
             capital_cost=costs.at["BtL", "fixed"],
-            marginal_cost=costs.at["BtL", "efficiency"] * costs.loc["BtL", "VOM"],
+            marginal_cost=costs.at["BtL", "efficiency"] * costs.at["BtL", "VOM"],
         )
 
         # TODO: Update with energy penalty
@@ -2371,7 +2373,7 @@ def add_biomass(n, costs):
             p_nom_extendable=True,
             capital_cost=costs.at["BtL", "fixed"]
             + costs.at["biomass CHP capture", "fixed"] * costs.at["BtL", "CO2 stored"],
-            marginal_cost=costs.at["BtL", "efficiency"] * costs.loc["BtL", "VOM"],
+            marginal_cost=costs.at["BtL", "efficiency"] * costs.at["BtL", "VOM"],
         )
 
     # BioSNG from solid biomass
@@ -2390,7 +2392,7 @@ def add_biomass(n, costs):
             + costs.at["BioSNG", "CO2 stored"],
             p_nom_extendable=True,
             capital_cost=costs.at["BioSNG", "fixed"],
-            marginal_cost=costs.at["BioSNG", "efficiency"] * costs.loc["BioSNG", "VOM"],
+            marginal_cost=costs.at["BioSNG", "efficiency"] * costs.at["BioSNG", "VOM"],
         )
 
         # TODO: Update with energy penalty for CC
@@ -2414,7 +2416,7 @@ def add_biomass(n, costs):
             capital_cost=costs.at["BioSNG", "fixed"]
             + costs.at["biomass CHP capture", "fixed"]
             * costs.at["BioSNG", "CO2 stored"],
-            marginal_cost=costs.at["BioSNG", "efficiency"] * costs.loc["BioSNG", "VOM"],
+            marginal_cost=costs.at["BioSNG", "efficiency"] * costs.at["BioSNG", "VOM"],
         )
 
 
@@ -2647,6 +2649,8 @@ def add_industry(n, costs):
             p_min_pu=options.get("min_part_load_methanolisation", 0),
             capital_cost=costs.at["methanolisation", "fixed"]
             * options["MWh_MeOH_per_MWh_H2"],  # EUR/MW_H2/a
+            marginal_cost=options["MWh_MeOH_per_MWh_H2"]
+            * costs.at["methanolisation", "VOM"],
             lifetime=costs.at["methanolisation", "lifetime"],
             efficiency=options["MWh_MeOH_per_MWh_H2"],
             efficiency2=-options["MWh_MeOH_per_MWh_H2"] / options["MWh_MeOH_per_MWh_e"],
@@ -2764,6 +2768,8 @@ def add_industry(n, costs):
         efficiency=costs.at["Fischer-Tropsch", "efficiency"],
         capital_cost=costs.at["Fischer-Tropsch", "fixed"]
         * costs.at["Fischer-Tropsch", "efficiency"],  # EUR/MW_H2/a
+        marginal_cost=costs.at["Fischer-Tropsch", "efficiency"]
+        * costs.at["Fischer-Tropsch", "VOM"],
         efficiency2=-costs.at["oil", "CO2 intensity"]
         * costs.at["Fischer-Tropsch", "efficiency"],
         p_nom_extendable=True,