diff --git a/homeassistant/components/iotawatt/sensor.py b/homeassistant/components/iotawatt/sensor.py
index acc4577fa8a..c3c173f778e 100644
--- a/homeassistant/components/iotawatt/sensor.py
+++ b/homeassistant/components/iotawatt/sensor.py
@@ -8,7 +8,6 @@ import logging
 from iotawattpy.sensor import Sensor
 
 from homeassistant.components.sensor import (
-    ATTR_LAST_RESET,
     SensorDeviceClass,
     SensorEntity,
     SensorEntityDescription,
@@ -211,6 +210,12 @@ class IotaWattSensor(update_coordinator.CoordinatorEntity, SensorEntity):
             else:
                 self.hass.async_create_task(self.async_remove())
             return
+
+        if (begin := self._sensor_data.getBegin()) and (
+            last_reset := dt.parse_datetime(begin)
+        ):
+            self._attr_last_reset = last_reset
+
         super()._handle_coordinator_update()
 
     @property
@@ -220,8 +225,6 @@ class IotaWattSensor(update_coordinator.CoordinatorEntity, SensorEntity):
         attrs = {"type": data.getType()}
         if attrs["type"] == "Input":
             attrs["channel"] = data.getChannel()
-        if (begin := data.getBegin()) and (last_reset := dt.parse_datetime(begin)):
-            attrs[ATTR_LAST_RESET] = last_reset.isoformat()
 
         return attrs