diff --git a/doc/release_notes.rst b/doc/release_notes.rst
index bf9860c6..685f8502 100644
--- a/doc/release_notes.rst
+++ b/doc/release_notes.rst
@@ -10,6 +10,8 @@ Release Notes
 Upcoming Release
 ================
 
+* Remove long-deprecated function ``attach_extendable_generators`` in :mod:`add_electricity`.
+
 * Upgrade techno-economic assumptions to ``technology-data`` v0.7.0.
 
 * Bugfix: Correct technology keys for the electricity production plotting to work out the box.
diff --git a/scripts/add_electricity.py b/scripts/add_electricity.py
index 9fd7e4a5..ab97dcd0 100755
--- a/scripts/add_electricity.py
+++ b/scripts/add_electricity.py
@@ -662,77 +662,6 @@ def attach_hydro(n, costs, ppl, profile_hydro, hydro_capacities, carriers, **par
         )
 
 
-def attach_extendable_generators(n, costs, ppl, carriers):
-    logger.warning(
-        "The function `attach_extendable_generators` is deprecated in v0.5.0."
-    )
-    add_missing_carriers(n, carriers)
-    add_co2_emissions(n, costs, carriers)
-
-    for tech in carriers:
-        if tech.startswith("OCGT"):
-            ocgt = (
-                ppl.query("carrier in ['OCGT', 'CCGT']")
-                .groupby("bus", as_index=False)
-                .first()
-            )
-            n.madd(
-                "Generator",
-                ocgt.index,
-                suffix=" OCGT",
-                bus=ocgt["bus"],
-                carrier=tech,
-                p_nom_extendable=True,
-                p_nom=0.0,
-                capital_cost=costs.at["OCGT", "capital_cost"],
-                marginal_cost=costs.at["OCGT", "marginal_cost"],
-                efficiency=costs.at["OCGT", "efficiency"],
-            )
-
-        elif tech.startswith("CCGT"):
-            ccgt = (
-                ppl.query("carrier in ['OCGT', 'CCGT']")
-                .groupby("bus", as_index=False)
-                .first()
-            )
-            n.madd(
-                "Generator",
-                ccgt.index,
-                suffix=" CCGT",
-                bus=ccgt["bus"],
-                carrier=tech,
-                p_nom_extendable=True,
-                p_nom=0.0,
-                capital_cost=costs.at["CCGT", "capital_cost"],
-                marginal_cost=costs.at["CCGT", "marginal_cost"],
-                efficiency=costs.at["CCGT", "efficiency"],
-            )
-
-        elif tech.startswith("nuclear"):
-            nuclear = (
-                ppl.query("carrier == 'nuclear'").groupby("bus", as_index=False).first()
-            )
-            n.madd(
-                "Generator",
-                nuclear.index,
-                suffix=" nuclear",
-                bus=nuclear["bus"],
-                carrier=tech,
-                p_nom_extendable=True,
-                p_nom=0.0,
-                capital_cost=costs.at["nuclear", "capital_cost"],
-                marginal_cost=costs.at["nuclear", "marginal_cost"],
-                efficiency=costs.at["nuclear", "efficiency"],
-            )
-
-        else:
-            raise NotImplementedError(
-                "Adding extendable generators for carrier "
-                "'{tech}' is not implemented, yet. "
-                "Only OCGT, CCGT and nuclear are allowed at the moment."
-            )
-
-
 def attach_OPSD_renewables(n: pypsa.Network, tech_map: Dict[str, List[str]]) -> None:
     """
     Attach renewable capacities from the OPSD dataset to the network.