diff --git a/homeassistant/components/shelly/entity.py b/homeassistant/components/shelly/entity.py
index a1ce2e671d1..0d23f5abffc 100644
--- a/homeassistant/components/shelly/entity.py
+++ b/homeassistant/components/shelly/entity.py
@@ -285,7 +285,6 @@ class ShellyBlockAttributeEntity(ShellyBlockEntity, entity.Entity):
         self._unit: None | str | Callable[[dict], str] = unit
         self._unique_id: str = f"{super().unique_id}-{self.attribute}"
         self._name = get_entity_name(wrapper.device, block, self.description.name)
-        self._last_value: str | None = None
 
     @property
     def unique_id(self) -> str:
diff --git a/homeassistant/components/shelly/sensor.py b/homeassistant/components/shelly/sensor.py
index 56e4f63bc75..07e4f4a4fe3 100644
--- a/homeassistant/components/shelly/sensor.py
+++ b/homeassistant/components/shelly/sensor.py
@@ -1,9 +1,12 @@
 """Sensor for Shelly."""
 from __future__ import annotations
 
-from datetime import datetime
+from datetime import timedelta
+import logging
 from typing import Final, cast
 
+import aioshelly
+
 from homeassistant.components import sensor
 from homeassistant.components.sensor import SensorEntity
 from homeassistant.config_entries import ConfigEntry
@@ -23,6 +26,7 @@ from homeassistant.helpers.entity_platform import AddEntitiesCallback
 from homeassistant.helpers.typing import StateType
 from homeassistant.util import dt
 
+from . import ShellyDeviceWrapper
 from .const import LAST_RESET_NEVER, LAST_RESET_UPTIME, SHAIR_MAX_WORK_HOURS
 from .entity import (
     BlockAttributeDescription,
@@ -35,6 +39,8 @@ from .entity import (
 )
 from .utils import get_device_uptime, temperature_unit
 
+_LOGGER: Final = logging.getLogger(__name__)
+
 SENSORS: Final = {
     ("device", "battery"): BlockAttributeDescription(
         name="Battery",
@@ -255,9 +261,39 @@ async def async_setup_entry(
 class ShellySensor(ShellyBlockAttributeEntity, SensorEntity):
     """Represent a shelly sensor."""
 
+    def __init__(
+        self,
+        wrapper: ShellyDeviceWrapper,
+        block: aioshelly.Block,
+        attribute: str,
+        description: BlockAttributeDescription,
+    ) -> None:
+        """Initialize sensor."""
+        super().__init__(wrapper, block, attribute, description)
+        self._last_value: float | None = None
+
+        if description.last_reset == LAST_RESET_NEVER:
+            self._attr_last_reset = dt.utc_from_timestamp(0)
+        elif description.last_reset == LAST_RESET_UPTIME:
+            self._attr_last_reset = (
+                dt.utcnow() - timedelta(seconds=wrapper.device.status["uptime"])
+            ).replace(second=0, microsecond=0)
+
     @property
     def state(self) -> StateType:
         """Return value of sensor."""
+        if (
+            self.description.last_reset == LAST_RESET_UPTIME
+            and self.attribute_value is not None
+        ):
+            value = cast(float, self.attribute_value)
+
+            if self._last_value and self._last_value > value:
+                self._attr_last_reset = dt.utcnow().replace(second=0, microsecond=0)
+                _LOGGER.info("Energy reset detected for entity %s", self.name)
+
+            self._last_value = value
+
         return self.attribute_value
 
     @property
@@ -265,20 +301,6 @@ class ShellySensor(ShellyBlockAttributeEntity, SensorEntity):
         """State class of sensor."""
         return self.description.state_class
 
-    @property
-    def last_reset(self) -> datetime | None:
-        """State class of sensor."""
-        if self.description.last_reset == LAST_RESET_UPTIME:
-            self._last_value = get_device_uptime(
-                self.wrapper.device.status, self._last_value
-            )
-            return dt.parse_datetime(self._last_value)
-
-        if self.description.last_reset == LAST_RESET_NEVER:
-            return dt.utc_from_timestamp(0)
-
-        return None
-
     @property
     def unit_of_measurement(self) -> str | None:
         """Return unit of sensor."""