diff --git a/homeassistant/components/watergate/sensor.py b/homeassistant/components/watergate/sensor.py
index 638bf297415..6782a93541b 100644
--- a/homeassistant/components/watergate/sensor.py
+++ b/homeassistant/components/watergate/sensor.py
@@ -90,7 +90,7 @@ DESCRIPTIONS: list[WatergateSensorEntityDescription] = [
     WatergateSensorEntityDescription(
         value_fn=lambda data: (
             dt_util.as_utc(
-                dt_util.now() - timedelta(microseconds=data.networking.wifi_uptime)
+                dt_util.now() - timedelta(milliseconds=data.networking.wifi_uptime)
             )
             if data.networking
             else None
@@ -104,7 +104,7 @@ DESCRIPTIONS: list[WatergateSensorEntityDescription] = [
     WatergateSensorEntityDescription(
         value_fn=lambda data: (
             dt_util.as_utc(
-                dt_util.now() - timedelta(microseconds=data.networking.mqtt_uptime)
+                dt_util.now() - timedelta(milliseconds=data.networking.mqtt_uptime)
             )
             if data.networking
             else None
@@ -158,7 +158,11 @@ DESCRIPTIONS: list[WatergateSensorEntityDescription] = [
     ),
     WatergateSensorEntityDescription(
         value_fn=lambda data: (
-            PowerSupplyMode(data.state.power_supply.replace("+", "_"))
+            PowerSupplyMode(
+                data.state.power_supply.replace("+", "_").replace(
+                    "external_battery", "battery_external"
+                )
+            )
             if data.state
             else None
         ),
diff --git a/tests/components/watergate/snapshots/test_sensor.ambr b/tests/components/watergate/snapshots/test_sensor.ambr
index 479a879a583..a58c7c0eab8 100644
--- a/tests/components/watergate/snapshots/test_sensor.ambr
+++ b/tests/components/watergate/snapshots/test_sensor.ambr
@@ -43,7 +43,7 @@
     'last_changed': <ANY>,
     'last_reported': <ANY>,
     'last_updated': <ANY>,
-    'state': '2021-01-09T11:59:59+00:00',
+    'state': '2021-01-09T11:59:58+00:00',
   })
 # ---
 # name: test_sensor[sensor.sonic_power_supply_mode-entry]
@@ -501,6 +501,6 @@
     'last_changed': <ANY>,
     'last_reported': <ANY>,
     'last_updated': <ANY>,
-    'state': '2021-01-09T11:59:59+00:00',
+    'state': '2021-01-09T11:59:57+00:00',
   })
 # ---
diff --git a/tests/components/watergate/test_sensor.py b/tests/components/watergate/test_sensor.py
index 58632c7548b..78e375857ed 100644
--- a/tests/components/watergate/test_sensor.py
+++ b/tests/components/watergate/test_sensor.py
@@ -140,11 +140,11 @@ async def test_power_supply_webhook(
 
     power_supply_change_data = {
         "type": "power-supply-changed",
-        "data": {"supply": "external"},
+        "data": {"supply": "external_battery"},
     }
     client = await hass_client_no_auth()
     await client.post(f"/api/webhook/{MOCK_WEBHOOK_ID}", json=power_supply_change_data)
 
     await hass.async_block_till_done()
 
-    assert hass.states.get(entity_id).state == "external"
+    assert hass.states.get(entity_id).state == "battery_external"