diff --git a/homeassistant/components/demo/climate.py b/homeassistant/components/demo/climate.py
index 666323d80d9..a7caede9b2d 100644
--- a/homeassistant/components/demo/climate.py
+++ b/homeassistant/components/demo/climate.py
@@ -45,7 +45,6 @@ async def async_setup_entry(
                 swing_mode=None,
                 hvac_mode=HVACMode.HEAT,
                 hvac_action=HVACAction.HEATING,
-                aux=None,
                 target_temp_high=None,
                 target_temp_low=None,
                 hvac_modes=[HVACMode.HEAT, HVACMode.OFF],
@@ -63,7 +62,6 @@ async def async_setup_entry(
                 swing_mode="off",
                 hvac_mode=HVACMode.COOL,
                 hvac_action=HVACAction.COOLING,
-                aux=False,
                 target_temp_high=None,
                 target_temp_low=None,
                 hvac_modes=[cls for cls in HVACMode if cls != HVACMode.HEAT_COOL],
@@ -82,7 +80,6 @@ async def async_setup_entry(
                 swing_mode="auto",
                 hvac_mode=HVACMode.HEAT_COOL,
                 hvac_action=None,
-                aux=None,
                 target_temp_high=24,
                 target_temp_low=21,
                 hvac_modes=[cls for cls in HVACMode if cls != HVACMode.HEAT],
@@ -114,7 +111,6 @@ class DemoClimate(ClimateEntity):
         swing_mode: str | None,
         hvac_mode: HVACMode,
         hvac_action: HVACAction | None,
-        aux: bool | None,
         target_temp_high: float | None,
         target_temp_low: float | None,
         hvac_modes: list[HVACMode],
@@ -133,8 +129,6 @@ class DemoClimate(ClimateEntity):
             self._attr_supported_features |= ClimateEntityFeature.TARGET_HUMIDITY
         if swing_mode is not None:
             self._attr_supported_features |= ClimateEntityFeature.SWING_MODE
-        if aux is not None:
-            self._attr_supported_features |= ClimateEntityFeature.AUX_HEAT
         if HVACMode.HEAT_COOL in hvac_modes or HVACMode.AUTO in hvac_modes:
             self._attr_supported_features |= (
                 ClimateEntityFeature.TARGET_TEMPERATURE_RANGE
@@ -152,7 +146,6 @@ class DemoClimate(ClimateEntity):
         self._current_fan_mode = fan_mode
         self._hvac_action = hvac_action
         self._hvac_mode = hvac_mode
-        self._aux = aux
         self._current_swing_mode = swing_mode
         self._fan_modes = ["on_low", "on_high", "auto_low", "auto_high", "off"]
         self._hvac_modes = hvac_modes
@@ -229,11 +222,6 @@ class DemoClimate(ClimateEntity):
         """Return preset modes."""
         return self._preset_modes
 
-    @property
-    def is_aux_heat(self) -> bool | None:
-        """Return true if aux heat is on."""
-        return self._aux
-
     @property
     def fan_mode(self) -> str | None:
         """Return the fan setting."""
@@ -292,13 +280,3 @@ class DemoClimate(ClimateEntity):
         """Update preset_mode on."""
         self._preset = preset_mode
         self.async_write_ha_state()
-
-    async def async_turn_aux_heat_on(self) -> None:
-        """Turn auxiliary heater on."""
-        self._aux = True
-        self.async_write_ha_state()
-
-    async def async_turn_aux_heat_off(self) -> None:
-        """Turn auxiliary heater off."""
-        self._aux = False
-        self.async_write_ha_state()
diff --git a/tests/components/demo/test_climate.py b/tests/components/demo/test_climate.py
index 11e9b9c01dd..dc2bdc3c720 100644
--- a/tests/components/demo/test_climate.py
+++ b/tests/components/demo/test_climate.py
@@ -6,7 +6,6 @@ import pytest
 import voluptuous as vol
 
 from homeassistant.components.climate import (
-    ATTR_AUX_HEAT,
     ATTR_CURRENT_HUMIDITY,
     ATTR_CURRENT_TEMPERATURE,
     ATTR_FAN_MODE,
@@ -25,7 +24,6 @@ from homeassistant.components.climate import (
     DOMAIN,
     PRESET_AWAY,
     PRESET_ECO,
-    SERVICE_SET_AUX_HEAT,
     SERVICE_SET_FAN_MODE,
     SERVICE_SET_HUMIDITY,
     SERVICE_SET_HVAC_MODE,
@@ -40,8 +38,6 @@ from homeassistant.const import (
     ATTR_TEMPERATURE,
     SERVICE_TURN_OFF,
     SERVICE_TURN_ON,
-    STATE_OFF,
-    STATE_ON,
     Platform,
 )
 from homeassistant.core import HomeAssistant
@@ -81,7 +77,6 @@ def test_setup_params(hass: HomeAssistant) -> None:
     assert state.attributes.get(ATTR_HUMIDITY) == 67
     assert state.attributes.get(ATTR_CURRENT_HUMIDITY) == 54
     assert state.attributes.get(ATTR_SWING_MODE) == "off"
-    assert state.attributes.get(ATTR_AUX_HEAT) == STATE_OFF
     assert state.attributes.get(ATTR_HVAC_MODES) == [
         HVACMode.OFF,
         HVACMode.HEAT,
@@ -384,49 +379,6 @@ async def test_set_hold_mode_eco(hass: HomeAssistant) -> None:
     assert state.attributes.get(ATTR_PRESET_MODE) == PRESET_ECO
 
 
-async def test_set_aux_heat_bad_attr(hass: HomeAssistant) -> None:
-    """Test setting the auxiliary heater without required attribute."""
-    state = hass.states.get(ENTITY_CLIMATE)
-    assert state.attributes.get(ATTR_AUX_HEAT) == STATE_OFF
-
-    with pytest.raises(vol.Invalid):
-        await hass.services.async_call(
-            DOMAIN,
-            SERVICE_SET_AUX_HEAT,
-            {ATTR_ENTITY_ID: ENTITY_CLIMATE, ATTR_AUX_HEAT: None},
-            blocking=True,
-        )
-
-    state = hass.states.get(ENTITY_CLIMATE)
-    assert state.attributes.get(ATTR_AUX_HEAT) == STATE_OFF
-
-
-async def test_set_aux_heat_on(hass: HomeAssistant) -> None:
-    """Test setting the axillary heater on/true."""
-    await hass.services.async_call(
-        DOMAIN,
-        SERVICE_SET_AUX_HEAT,
-        {ATTR_ENTITY_ID: ENTITY_CLIMATE, ATTR_AUX_HEAT: True},
-        blocking=True,
-    )
-
-    state = hass.states.get(ENTITY_CLIMATE)
-    assert state.attributes.get(ATTR_AUX_HEAT) == STATE_ON
-
-
-async def test_set_aux_heat_off(hass: HomeAssistant) -> None:
-    """Test setting the auxiliary heater off/false."""
-    await hass.services.async_call(
-        DOMAIN,
-        SERVICE_SET_AUX_HEAT,
-        {ATTR_ENTITY_ID: ENTITY_CLIMATE, ATTR_AUX_HEAT: False},
-        blocking=True,
-    )
-
-    state = hass.states.get(ENTITY_CLIMATE)
-    assert state.attributes.get(ATTR_AUX_HEAT) == STATE_OFF
-
-
 async def test_turn_on(hass: HomeAssistant) -> None:
     """Test turn on device."""
     await hass.services.async_call(