diff --git a/homeassistant/components/mill/climate.py b/homeassistant/components/mill/climate.py
index 03ec18a50b3..a6cfbb8cb7a 100644
--- a/homeassistant/components/mill/climate.py
+++ b/homeassistant/components/mill/climate.py
@@ -105,7 +105,7 @@ class MillHeater(CoordinatorEntity, ClimateEntity):
             model=f"Generation {heater.generation}",
             name=self.name,
         )
-        if heater.is_gen1 or heater.is_gen3:
+        if heater.is_gen1:
             self._attr_hvac_modes = [HVAC_MODE_HEAT]
         else:
             self._attr_hvac_modes = [HVAC_MODE_HEAT, HVAC_MODE_OFF]