diff --git a/homeassistant/components/fritzbox/coordinator.py b/homeassistant/components/fritzbox/coordinator.py
index 8a37ebf63e4..a95af62da6c 100644
--- a/homeassistant/components/fritzbox/coordinator.py
+++ b/homeassistant/components/fritzbox/coordinator.py
@@ -171,14 +171,19 @@ class FritzboxDataUpdateCoordinator(DataUpdateCoordinator[FritzboxCoordinatorDat
 
         for device in new_data.devices.values():
             # create device registry entry for new main devices
-            if (
-                device.ain not in self.data.devices
-                and device.device_and_unit_id[1] is None
+            if device.ain not in self.data.devices and (
+                device.device_and_unit_id[1] is None
+                or (
+                    # workaround for sub units without a main device, e.g. Energy 250
+                    # https://github.com/home-assistant/core/issues/145204
+                    device.device_and_unit_id[1] == "1"
+                    and device.device_and_unit_id[0] not in new_data.devices
+                )
             ):
                 dr.async_get(self.hass).async_get_or_create(
                     config_entry_id=self.config_entry.entry_id,
                     name=device.name,
-                    identifiers={(DOMAIN, device.ain)},
+                    identifiers={(DOMAIN, device.device_and_unit_id[0])},
                     manufacturer=device.manufacturer,
                     model=device.productname,
                     sw_version=device.fw_version,
diff --git a/tests/components/fritzbox/test_coordinator.py b/tests/components/fritzbox/test_coordinator.py
index 61de0c99940..794d6ac4397 100644
--- a/tests/components/fritzbox/test_coordinator.py
+++ b/tests/components/fritzbox/test_coordinator.py
@@ -15,7 +15,12 @@ from homeassistant.core import HomeAssistant
 from homeassistant.helpers import device_registry as dr, entity_registry as er
 from homeassistant.util.dt import utcnow
 
-from . import FritzDeviceCoverMock, FritzDeviceSwitchMock, FritzEntityBaseMock
+from . import (
+    FritzDeviceCoverMock,
+    FritzDeviceSensorMock,
+    FritzDeviceSwitchMock,
+    FritzEntityBaseMock,
+)
 from .const import MOCK_CONFIG
 
 from tests.common import MockConfigEntry, async_fire_time_changed
@@ -140,3 +145,42 @@ async def test_coordinator_automatic_registry_cleanup(
 
     assert len(er.async_entries_for_config_entry(entity_registry, entry.entry_id)) == 12
     assert len(dr.async_entries_for_config_entry(device_registry, entry.entry_id)) == 1
+
+
+async def test_coordinator_workaround_sub_units_without_main_device(
+    hass: HomeAssistant,
+    fritz: Mock,
+    device_registry: dr.DeviceRegistry,
+) -> None:
+    """Test the workaround for sub units without main device."""
+    fritz().get_devices.return_value = [
+        FritzDeviceSensorMock(
+            ain="bad_device-1",
+            device_and_unit_id=("bad_device", "1"),
+            name="bad_sensor_sub",
+        ),
+        FritzDeviceSensorMock(
+            ain="good_device",
+            device_and_unit_id=("good_device", None),
+            name="good_sensor",
+        ),
+        FritzDeviceSensorMock(
+            ain="good_device-1",
+            device_and_unit_id=("good_device", "1"),
+            name="good_sensor_sub",
+        ),
+    ]
+
+    entry = MockConfigEntry(
+        domain=DOMAIN,
+        data=MOCK_CONFIG[DOMAIN][CONF_DEVICES][0],
+        unique_id="any",
+    )
+    entry.add_to_hass(hass)
+    await hass.config_entries.async_setup(entry.entry_id)
+    await hass.async_block_till_done(wait_background_tasks=True)
+
+    device_entries = dr.async_entries_for_config_entry(device_registry, entry.entry_id)
+    assert len(device_entries) == 2
+    assert device_entries[0].identifiers == {(DOMAIN, "good_device")}
+    assert device_entries[1].identifiers == {(DOMAIN, "bad_device")}