Determine zwave_js sensor device class during initialization (#48304)

homeassistant/components/zwave_js/sensor.py

@@ -80,10 +80,15 @@ class ZwaveSensorBase(ZWaveBaseEntity, SensorEntity):
         """Initialize a ZWaveSensorBase entity."""
         super().__init__(config_entry, client, info)
         self._name = self.generate_name(include_value_name=True)
+        self._device_class = self._get_device_class()
 
-    @property
+    def _get_device_class(self) -> str | None:
-    def device_class(self) -> str | None:
+        """
-        """Return the device class of the sensor."""
+        Get the device class of the sensor.
+
+        This should be run once during initialization so we don't have to calculate
+        this value on every state update.
+        """
         if self.info.primary_value.command_class == CommandClass.BATTERY:
             return DEVICE_CLASS_BATTERY
         if self.info.primary_value.command_class == CommandClass.METER:
@@ -102,6 +107,11 @@ class ZwaveSensorBase(ZWaveBaseEntity, SensorEntity):
             return DEVICE_CLASS_ILLUMINANCE
         return None
 
+    @property
+    def device_class(self) -> str | None:
+        """Return the device class of the sensor."""
+        return self._device_class
+
     @property
     def entity_registry_enabled_default(self) -> bool:
         """Return if the entity should be enabled when first added to the entity registry."""