diff --git a/custom_components/powercalc/config_flow.py b/custom_components/powercalc/config_flow.py
index 65d6922a5..2dafb7114 100644
--- a/custom_components/powercalc/config_flow.py
+++ b/custom_components/powercalc/config_flow.py
@@ -1034,7 +1034,7 @@ async def _create_schema(
         ) -> vol.Schema:
             """Create sub profile schema."""
             library = await ProfileLibrary.factory(self.hass)
-            profile = await library.get_profile(model_info)
+            profile = await library.get_profile(model_info, process_variables=False)
             sub_profiles = [selector.SelectOptionDict(value=sub_profile, label=sub_profile) for sub_profile in await profile.get_sub_profiles()]
             return vol.Schema(
                 {
diff --git a/custom_components/powercalc/discovery.py b/custom_components/powercalc/discovery.py
index e33b7c61a..2a50c7c3a 100644
--- a/custom_components/powercalc/discovery.py
+++ b/custom_components/powercalc/discovery.py
@@ -51,7 +51,7 @@ async def get_power_profile_by_source_entity(hass: HomeAssistant, source_entity:
     model_info = await discovery_manager.extract_model_info_from_device_info(source_entity.entity_entry)
     if not model_info:
         return None
-    profiles = await discovery_manager.discover_entity(source_entity, model_info)
+    profiles = await discovery_manager.find_power_profiles(model_info, source_entity, DiscoveryBy.ENTITY)
     return profiles[0] if profiles else None
 
 
@@ -203,7 +203,7 @@ async def find_power_profiles(
 
         power_profiles = []
         for model_info in models:
-            profile = await get_power_profile(self.hass, {}, model_info=model_info)
+            profile = await get_power_profile(self.hass, {}, model_info=model_info, process_variables=False)
             if not profile or profile.discovery_by != discovery_type:  # pragma: no cover
                 continue
             if discovery_type == DiscoveryBy.ENTITY and not await self.is_entity_supported(
@@ -266,6 +266,7 @@ async def is_entity_supported(
                     {},
                     model_info,
                     log_errors=log_profile_loading_errors,
+                    process_variables=False,
                 )
             except ModelNotSupportedError:
                 return False
diff --git a/custom_components/powercalc/power_profile/factory.py b/custom_components/powercalc/power_profile/factory.py
index e69b5d8d7..55b665658 100644
--- a/custom_components/powercalc/power_profile/factory.py
+++ b/custom_components/powercalc/power_profile/factory.py
@@ -26,6 +26,7 @@ async def get_power_profile(
     config: dict,
     model_info: ModelInfo | None = None,
     log_errors: bool = True,
+    process_variables: bool = True,
 ) -> PowerProfile | None:
     manufacturer = config.get(CONF_MANUFACTURER)
     model = config.get(CONF_MODEL)
@@ -55,6 +56,7 @@ async def get_power_profile(
             ModelInfo(manufacturer or "", model or "", model_id),
             custom_model_directory,
             config.get(CONF_CUSTOM_FIELDS),
+            process_variables,
         )
     except LibraryError as err:
         if log_errors:
diff --git a/custom_components/powercalc/power_profile/library.py b/custom_components/powercalc/power_profile/library.py
index 004335337..84224a863 100644
--- a/custom_components/powercalc/power_profile/library.py
+++ b/custom_components/powercalc/power_profile/library.py
@@ -3,7 +3,7 @@
 import logging
 import os
 import re
-from typing import NamedTuple, cast
+from typing import Any, NamedTuple, cast
 
 from homeassistant.core import HomeAssistant
 from homeassistant.helpers.singleton import singleton
@@ -98,6 +98,7 @@ async def get_profile(
         model_info: ModelInfo,
         custom_directory: str | None = None,
         variables: dict[str, str] | None = None,
+        process_variables: bool = True,
     ) -> PowerProfile:
         """Get a power profile for a given manufacturer and model."""
         # Support multiple LUT in subdirectories
@@ -106,7 +107,7 @@ async def get_profile(
             (model, sub_profile) = model_info.model.split("/", 1)
             model_info = ModelInfo(model_info.manufacturer, model, model_info.model_id)
 
-        profile = await self.create_power_profile(model_info, custom_directory, variables)
+        profile = await self.create_power_profile(model_info, custom_directory, variables, process_variables)
 
         if sub_profile:
             await profile.select_sub_profile(sub_profile)
@@ -118,6 +119,7 @@ async def create_power_profile(
         model_info: ModelInfo,
         custom_directory: str | None = None,
         variables: dict[str, str] | None = None,
+        process_variables: bool = True,
     ) -> PowerProfile:
         """Create a power profile object from the model JSON data."""
 
@@ -128,14 +130,29 @@ async def create_power_profile(
             model_info = next(iter(models))
 
         json_data, directory = await self._load_model_data(model_info.manufacturer, model_info.model, custom_directory)
-        if variables:
-            json_data = cast(dict, replace_placeholders(json_data, variables))
+        if json_data.get("fields") and process_variables:
+            self.validate_variables(json_data, variables or {})
+            json_data = cast(dict, replace_placeholders(json_data, variables or {}))
         if linked_profile := json_data.get("linked_profile", json_data.get("linked_lut")):
             linked_manufacturer, linked_model = linked_profile.split("/")
             _, directory = await self._load_model_data(linked_manufacturer, linked_model, custom_directory)
 
         return await self._create_power_profile_instance(model_info.manufacturer, model_info.model, directory, json_data)
 
+    @staticmethod
+    def validate_variables(json_data: dict[str, Any], variables: dict[str, str]) -> None:
+        fields = json_data.get("fields", {}).keys()
+
+        # Check if all variables are valid for the model
+        for variable in variables:
+            if variable not in fields:
+                raise LibraryError(f"Variable {variable} is not valid for this model")
+
+        # Check if all fields have corresponding variables
+        missing_fields = [field for field in fields if field not in variables]
+        if missing_fields:
+            raise LibraryError(f"Missing variables for fields: {', '.join(missing_fields)}")
+
     async def find_manufacturers(self, manufacturer: str) -> set[str]:
         """Resolve the manufacturer, either from the model info or by loading it."""
         return await self._loader.find_manufacturers(manufacturer)
diff --git a/custom_components/powercalc/sensor.py b/custom_components/powercalc/sensor.py
index f18d90129..97df4cebd 100644
--- a/custom_components/powercalc/sensor.py
+++ b/custom_components/powercalc/sensor.py
@@ -52,6 +52,7 @@
     CONF_CREATE_ENERGY_SENSOR,
     CONF_CREATE_GROUP,
     CONF_CREATE_UTILITY_METERS,
+    CONF_CUSTOM_FIELDS,
     CONF_CUSTOM_MODEL_DIRECTORY,
     CONF_DAILY_FIXED_ENERGY,
     CONF_DELAY,
@@ -218,6 +219,7 @@
     ),
     vol.Optional(CONF_UNAVAILABLE_POWER): vol.Coerce(float),
     vol.Optional(CONF_COMPOSITE): COMPOSITE_SCHEMA,
+    vol.Optional(CONF_CUSTOM_FIELDS): vol.Schema({cv.string: cv.string}),
 }
 
 
diff --git a/tests/power_profile/device_types/test_custom_fields.py b/tests/power_profile/device_types/test_custom_fields.py
new file mode 100644
index 000000000..4505932f2
--- /dev/null
+++ b/tests/power_profile/device_types/test_custom_fields.py
@@ -0,0 +1,33 @@
+import logging
+
+import pytest
+from homeassistant.const import CONF_ENTITY_ID, CONF_NAME, STATE_ON
+from homeassistant.core import HomeAssistant
+
+from custom_components.powercalc.const import CONF_CUSTOM_FIELDS, CONF_MANUFACTURER, CONF_MODEL, DUMMY_ENTITY_ID
+from tests.common import get_test_config_dir, run_powercalc_setup
+
+
+async def test_custom_field_variables_from_yaml_config(hass: HomeAssistant, caplog: pytest.LogCaptureFixture) -> None:
+    caplog.set_level(logging.ERROR)
+    hass.config.config_dir = get_test_config_dir()
+
+    hass.states.async_set("sensor.test", STATE_ON)
+    await hass.async_block_till_done()
+
+    await run_powercalc_setup(
+        hass,
+        {
+            CONF_ENTITY_ID: DUMMY_ENTITY_ID,
+            CONF_NAME: "Test",
+            CONF_MANUFACTURER: "test",
+            CONF_MODEL: "custom-fields",
+            CONF_CUSTOM_FIELDS: {
+                "some_entity": "sensor.test",
+            },
+        },
+    )
+
+    assert not caplog.records
+
+    assert hass.states.get("sensor.test_power").state == "20.00"