diff --git a/homeassistant/components/nrgkick/sensor.py b/homeassistant/components/nrgkick/sensor.py
index 090a1f19c3f..680de893008 100644
--- a/homeassistant/components/nrgkick/sensor.py
+++ b/homeassistant/components/nrgkick/sensor.py
@@ -7,6 +7,8 @@ from dataclasses import dataclass
 from datetime import datetime, timedelta
 from typing import Any, cast
 
+from nrgkick_api import ChargingStatus
+
 from homeassistant.components.sensor import (
     SensorDeviceClass,
     SensorEntity,
@@ -632,11 +634,18 @@ SENSORS: tuple[NRGkickSensorEntityDescription, ...] = (
         key="vehicle_connected_since",
         translation_key="vehicle_connected_since",
         device_class=SensorDeviceClass.TIMESTAMP,
-        value_fn=lambda data: _seconds_to_stable_timestamp(
-            cast(
-                StateType,
-                _get_nested_dict_value(data.values, "general", "vehicle_connect_time"),
+        value_fn=lambda data: (
+            _seconds_to_stable_timestamp(
+                cast(
+                    StateType,
+                    _get_nested_dict_value(
+                        data.values, "general", "vehicle_connect_time"
+                    ),
+                )
             )
+            if _get_nested_dict_value(data.values, "general", "status")
+            != ChargingStatus.STANDBY
+            else None
         ),
     ),
     NRGkickSensorEntityDescription(
diff --git a/tests/components/nrgkick/test_sensor.py b/tests/components/nrgkick/test_sensor.py
index c8ab7d4a797..b84a59f752a 100644
--- a/tests/components/nrgkick/test_sensor.py
+++ b/tests/components/nrgkick/test_sensor.py
@@ -67,3 +67,19 @@ async def test_cellular_and_gps_entities_are_gated_by_model_type(
     assert hass.states.get("sensor.nrgkick_test_cellular_mode") is None
     assert hass.states.get("sensor.nrgkick_test_cellular_signal_strength") is None
     assert hass.states.get("sensor.nrgkick_test_cellular_operator") is None
+
+
+async def test_vehicle_connected_since_none_when_standby(
+    hass: HomeAssistant,
+    mock_config_entry: MockConfigEntry,
+    mock_nrgkick_api: AsyncMock,
+) -> None:
+    """Test vehicle connected since is unknown when vehicle is not connected."""
+    mock_nrgkick_api.get_values.return_value["general"]["status"] = (
+        ChargingStatus.STANDBY
+    )
+
+    await setup_integration(hass, mock_config_entry, platforms=[Platform.SENSOR])
+
+    assert (state := hass.states.get("sensor.nrgkick_test_vehicle_connected_since"))
+    assert state.state == STATE_UNKNOWN