diff --git a/homeassistant/components/shelly/config_flow.py b/homeassistant/components/shelly/config_flow.py
index 29daf0501637..59ae6eed1965 100644
--- a/homeassistant/components/shelly/config_flow.py
+++ b/homeassistant/components/shelly/config_flow.py
@@ -36,6 +36,7 @@ from .coordinator import async_reconnect_soon
 from .utils import (
     get_block_device_sleep_period,
     get_coap_context,
+    get_device_entry_gen,
     get_info_auth,
     get_info_gen,
     get_model_name,
@@ -322,7 +323,7 @@ class ShellyConfigFlow(ConfigFlow, domain=DOMAIN):
             except (DeviceConnectionError, InvalidAuthError, FirmwareUnsupported):
                 return self.async_abort(reason="reauth_unsuccessful")
 
-            if self.entry.data.get(CONF_GEN, 1) != 1:
+            if get_device_entry_gen(self.entry) != 1:
                 user_input[CONF_USERNAME] = "admin"
             try:
                 await validate_input(self.hass, host, info, user_input)
@@ -335,7 +336,7 @@ class ShellyConfigFlow(ConfigFlow, domain=DOMAIN):
             await self.hass.config_entries.async_reload(self.entry.entry_id)
             return self.async_abort(reason="reauth_successful")
 
-        if self.entry.data.get(CONF_GEN, 1) in BLOCK_GENERATIONS:
+        if get_device_entry_gen(self.entry) in BLOCK_GENERATIONS:
             schema = {
                 vol.Required(CONF_USERNAME): str,
                 vol.Required(CONF_PASSWORD): str,
@@ -364,7 +365,7 @@ class ShellyConfigFlow(ConfigFlow, domain=DOMAIN):
     def async_supports_options_flow(cls, config_entry: ConfigEntry) -> bool:
         """Return options flow support for this handler."""
         return (
-            config_entry.data.get(CONF_GEN) in RPC_GENERATIONS
+            get_device_entry_gen(config_entry) in RPC_GENERATIONS
             and not config_entry.data.get(CONF_SLEEP_PERIOD)
             and config_entry.data.get("model") != MODEL_WALL_DISPLAY
         )
diff --git a/homeassistant/components/shelly/coordinator.py b/homeassistant/components/shelly/coordinator.py
index 77fa0bd2efd1..7f88cce1134b 100644
--- a/homeassistant/components/shelly/coordinator.py
+++ b/homeassistant/components/shelly/coordinator.py
@@ -33,7 +33,6 @@ from .const import (
     ATTR_GENERATION,
     BATTERY_DEVICES_WITH_PERMANENT_CONNECTION,
     CONF_BLE_SCANNER_MODE,
-    CONF_GEN,
     CONF_SLEEP_PERIOD,
     DATA_CONFIG_ENTRY,
     DOMAIN,
@@ -58,7 +57,11 @@ from .const import (
     UPDATE_PERIOD_MULTIPLIER,
     BLEScannerMode,
 )
-from .utils import get_rpc_device_wakeup_period, update_device_fw_info
+from .utils import (
+    get_device_entry_gen,
+    get_rpc_device_wakeup_period,
+    update_device_fw_info,
+)
 
 _DeviceT = TypeVar("_DeviceT", bound="BlockDevice|RpcDevice")
 
@@ -136,7 +139,7 @@ class ShellyCoordinatorBase(DataUpdateCoordinator[None], Generic[_DeviceT]):
             manufacturer="Shelly",
             model=aioshelly.const.MODEL_NAMES.get(self.model, self.model),
             sw_version=self.sw_version,
-            hw_version=f"gen{self.entry.data[CONF_GEN]} ({self.model})",
+            hw_version=f"gen{get_device_entry_gen(self.entry)} ({self.model})",
             configuration_url=f"http://{self.entry.data[CONF_HOST]}",
         )
         self.device_id = device_entry.id
diff --git a/tests/components/shelly/__init__.py b/tests/components/shelly/__init__.py
index 0384e9255a38..26040e135577 100644
--- a/tests/components/shelly/__init__.py
+++ b/tests/components/shelly/__init__.py
@@ -12,6 +12,7 @@ from freezegun.api import FrozenDateTimeFactory
 import pytest
 
 from homeassistant.components.shelly.const import (
+    CONF_GEN,
     CONF_SLEEP_PERIOD,
     DOMAIN,
     REST_SENSORS_UPDATE_INTERVAL,
@@ -30,7 +31,7 @@ MOCK_MAC = "123456789ABC"
 
 async def init_integration(
     hass: HomeAssistant,
-    gen: int,
+    gen: int | None,
     model=MODEL_25,
     sleep_period=0,
     options: dict[str, Any] | None = None,
@@ -41,8 +42,9 @@ async def init_integration(
         CONF_HOST: "192.168.1.37",
         CONF_SLEEP_PERIOD: sleep_period,
         "model": model,
-        "gen": gen,
     }
+    if gen is not None:
+        data[CONF_GEN] = gen
 
     entry = MockConfigEntry(
         domain=DOMAIN, data=data, unique_id=MOCK_MAC, options=options
diff --git a/tests/components/shelly/test_init.py b/tests/components/shelly/test_init.py
index 8f6599b39e46..643fc775cc42 100644
--- a/tests/components/shelly/test_init.py
+++ b/tests/components/shelly/test_init.py
@@ -301,3 +301,11 @@ async def test_no_attempt_to_stop_scanner_with_sleepy_devices(
         mock_rpc_device.mock_update()
         await hass.async_block_till_done()
         assert not mock_stop_scanner.call_count
+
+
+async def test_entry_missing_gen(hass: HomeAssistant, mock_block_device) -> None:
+    """Test successful Gen1 device init when gen is missing in entry data."""
+    entry = await init_integration(hass, None)
+
+    assert entry.state is ConfigEntryState.LOADED
+    assert hass.states.get("switch.test_name_channel_1").state is STATE_ON