diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 8c5560a..095fa6d 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -49,8 +49,9 @@ repos:
     rev: v1.13.0
     hooks:
       - id: mypy
-        additional_dependencies: [pytest]
+        additional_dependencies: [pytest, homeassistant]
         args:
           - --pretty
           - --show-error-codes
-          - --show-error-context
\ No newline at end of file
+          - --show-error-context
+          - -v
\ No newline at end of file
diff --git a/custom_components/askoheat/config_flow.py b/custom_components/askoheat/config_flow.py
index 22d1685..c2528ff 100644
--- a/custom_components/askoheat/config_flow.py
+++ b/custom_components/askoheat/config_flow.py
@@ -7,9 +7,10 @@
 
 import homeassistant.helpers.config_validation as cv
 import voluptuous as vol
-from homeassistant import config_entries, data_entry_flow
+from homeassistant import data_entry_flow
 from homeassistant.components.sensor.const import SensorDeviceClass
 from homeassistant.config_entries import (
+    ConfigFlow,
     ConfigFlowResult,
     OptionsFlow,
     OptionsFlowWithConfigEntry,
@@ -108,7 +109,8 @@ def _step_user_data_schema(
                                 filter=selector.EntityFilterSelectorConfig(
                                     domain=Platform.SENSOR,
                                     device_class=SensorDeviceClass.POWER,
-                                )
+                                ),
+                                multiple=False,
                             )
                         ),
                         vol.Required(
@@ -194,7 +196,7 @@ def _step_user_data_schema(
 STEP_USER_DATA_SCHEMA = _step_user_data_schema()
 
 
-class AskoheatFlowHandler(config_entries.ConfigFlow, domain=DOMAIN):
+class AskoheatFlowHandler(ConfigFlow, domain=DOMAIN):
     """Config flow for Blueprint."""
 
     VERSION = 1
diff --git a/custom_components/askoheat/switch.py b/custom_components/askoheat/switch.py
index 5844417..2576b1e 100644
--- a/custom_components/askoheat/switch.py
+++ b/custom_components/askoheat/switch.py
@@ -6,6 +6,7 @@
 
 from homeassistant.components.switch import ENTITY_ID_FORMAT, SwitchEntity
 from homeassistant.core import Event, EventStateChangedData, HomeAssistant, callback
+from homeassistant.exceptions import ConfigEntryError
 from homeassistant.helpers.event import async_track_state_change_event
 
 from custom_components.askoheat.api_conf_desc import (
@@ -78,7 +79,10 @@ def config_power_entity() -> str | None:
         if entity_description.device_key is None
         or entity_description.device_key in entry.runtime_data.supported_devices
     )
-    if power_entity_id is not None:
+    if power_entity_id is not None and power_entity_id != []:
+        if isinstance(power_entity_id, list) and len(power_entity_id) != 1:
+            msg = "Cannot track multiple power_entities"
+            raise ConfigEntryError(msg)
 
         def config_power_invert() -> bool | None:
             dev = entry.data.get(CONF_FEED_IN)