diff --git a/homeassistant/components/generic_thermostat/climate.py b/homeassistant/components/generic_thermostat/climate.py
index a659d13cb7e..c48deba12d8 100644
--- a/homeassistant/components/generic_thermostat/climate.py
+++ b/homeassistant/components/generic_thermostat/climate.py
@@ -227,6 +227,12 @@ class GenericThermostat(ClimateEntity, RestoreEntity):
             ):
                 self._async_update_temp(sensor_state)
                 self.async_write_ha_state()
+            switch_state = self.hass.states.get(self.heater_entity_id)
+            if switch_state and switch_state.state not in (
+                STATE_UNAVAILABLE,
+                STATE_UNKNOWN,
+            ):
+                self.hass.create_task(self._check_switch_initial_state())
 
         if self.hass.state == CoreState.running:
             _async_startup()
@@ -270,14 +276,6 @@ class GenericThermostat(ClimateEntity, RestoreEntity):
         if not self._hvac_mode:
             self._hvac_mode = HVAC_MODE_OFF
 
-        # Prevent the device from keep running if HVAC_MODE_OFF
-        if self._hvac_mode == HVAC_MODE_OFF and self._is_device_active:
-            await self._async_heater_turn_off()
-            _LOGGER.warning(
-                "The climate mode is OFF, but the switch device is ON. Turning off device %s",
-                self.heater_entity_id,
-            )
-
     @property
     def should_poll(self):
         """Return the polling state."""
@@ -401,12 +399,24 @@ class GenericThermostat(ClimateEntity, RestoreEntity):
         await self._async_control_heating()
         self.async_write_ha_state()
 
+    async def _check_switch_initial_state(self):
+        """Prevent the device from keep running if HVAC_MODE_OFF."""
+        if self._hvac_mode == HVAC_MODE_OFF and self._is_device_active:
+            _LOGGER.warning(
+                "The climate mode is OFF, but the switch device is ON. Turning off device %s",
+                self.heater_entity_id,
+            )
+            await self._async_heater_turn_off()
+
     @callback
     def _async_switch_changed(self, event):
         """Handle heater switch state changes."""
         new_state = event.data.get("new_state")
+        old_state = event.data.get("old_state")
         if new_state is None:
             return
+        if old_state is None:
+            self.hass.create_task(self._check_switch_initial_state())
         self.async_write_ha_state()
 
     @callback
@@ -426,7 +436,6 @@ class GenericThermostat(ClimateEntity, RestoreEntity):
             if not self._active and None not in (
                 self._cur_temp,
                 self._target_temp,
-                self._is_device_active,
             ):
                 self._active = True
                 _LOGGER.info(
diff --git a/tests/components/generic_thermostat/test_climate.py b/tests/components/generic_thermostat/test_climate.py
index 7363ee8a32a..4015887efbb 100644
--- a/tests/components/generic_thermostat/test_climate.py
+++ b/tests/components/generic_thermostat/test_climate.py
@@ -42,6 +42,7 @@ from homeassistant.util.unit_system import METRIC_SYSTEM
 from tests.common import (
     assert_setup_component,
     async_fire_time_changed,
+    async_mock_service,
     mock_restore_cache,
 )
 from tests.components.climate import common
@@ -1189,14 +1190,15 @@ async def test_custom_setup_params(hass):
     assert state.attributes.get("temperature") == TARGET_TEMP
 
 
-async def test_restore_state(hass):
+@pytest.mark.parametrize("hvac_mode", [HVAC_MODE_OFF, HVAC_MODE_HEAT, HVAC_MODE_COOL])
+async def test_restore_state(hass, hvac_mode):
     """Ensure states are restored on startup."""
     mock_restore_cache(
         hass,
         (
             State(
                 "climate.test_thermostat",
-                HVAC_MODE_OFF,
+                hvac_mode,
                 {ATTR_TEMPERATURE: "20", ATTR_PRESET_MODE: PRESET_AWAY},
             ),
         ),
@@ -1221,7 +1223,7 @@ async def test_restore_state(hass):
     state = hass.states.get("climate.test_thermostat")
     assert state.attributes[ATTR_TEMPERATURE] == 20
     assert state.attributes[ATTR_PRESET_MODE] == PRESET_AWAY
-    assert state.state == HVAC_MODE_OFF
+    assert state.state == hvac_mode
 
 
 async def test_no_restore_state(hass):
@@ -1347,6 +1349,66 @@ async def test_restore_will_turn_off_(hass):
     assert hass.states.get(heater_switch).state == STATE_ON
 
 
+async def test_restore_will_turn_off_when_loaded_second(hass):
+    """Ensure that restored state is coherent with real situation.
+
+    Switch is not available until after component is loaded
+    """
+    heater_switch = "input_boolean.test"
+    mock_restore_cache(
+        hass,
+        (
+            State(
+                "climate.test_thermostat",
+                HVAC_MODE_HEAT,
+                {ATTR_TEMPERATURE: "18", ATTR_PRESET_MODE: PRESET_NONE},
+            ),
+            State(heater_switch, STATE_ON, {}),
+        ),
+    )
+
+    hass.state = CoreState.starting
+
+    await hass.async_block_till_done()
+    assert hass.states.get(heater_switch) is None
+
+    _setup_sensor(hass, 16)
+
+    await async_setup_component(
+        hass,
+        DOMAIN,
+        {
+            "climate": {
+                "platform": "generic_thermostat",
+                "name": "test_thermostat",
+                "heater": heater_switch,
+                "target_sensor": ENT_SENSOR,
+                "target_temp": 20,
+                "initial_hvac_mode": HVAC_MODE_OFF,
+            }
+        },
+    )
+    await hass.async_block_till_done()
+    state = hass.states.get("climate.test_thermostat")
+    assert state.attributes[ATTR_TEMPERATURE] == 20
+    assert state.state == HVAC_MODE_OFF
+
+    calls_on = async_mock_service(hass, ha.DOMAIN, SERVICE_TURN_ON)
+    calls_off = async_mock_service(hass, ha.DOMAIN, SERVICE_TURN_OFF)
+
+    assert await async_setup_component(
+        hass, input_boolean.DOMAIN, {"input_boolean": {"test": None}}
+    )
+    await hass.async_block_till_done()
+    # heater must be switched off
+    assert len(calls_on) == 0
+    assert len(calls_off) == 1
+    call = calls_off[0]
+    assert call.domain == HASS_DOMAIN
+    assert call.service == SERVICE_TURN_OFF
+    assert call.data["entity_id"] == "input_boolean.test"
+
+
 async def test_restore_state_uncoherence_case(hass):
     """
     Test restore from a strange state.