diff --git a/homeassistant/components/integration/sensor.py b/homeassistant/components/integration/sensor.py
index e935dd5dc14..02451773558 100644
--- a/homeassistant/components/integration/sensor.py
+++ b/homeassistant/components/integration/sensor.py
@@ -5,7 +5,7 @@ from __future__ import annotations
 from abc import ABC, abstractmethod
 from dataclasses import dataclass
 from datetime import UTC, datetime, timedelta
-from decimal import Decimal, DecimalException, InvalidOperation
+from decimal import Decimal, InvalidOperation
 from enum import Enum
 import logging
 from typing import Any, Final, Self
@@ -27,7 +27,6 @@ from homeassistant.const import (
     CONF_NAME,
     CONF_UNIQUE_ID,
     STATE_UNAVAILABLE,
-    STATE_UNKNOWN,
     UnitOfTime,
 )
 from homeassistant.core import (
@@ -428,24 +427,6 @@ class IntegrationSensor(RestoreSensor):
                 self._state,
                 self._last_valid_state,
             )
-        elif (state := await self.async_get_last_state()) is not None:
-            # legacy to be removed on 2023.10 (we are keeping this to avoid losing data during the transition)
-            if state.state in [STATE_UNAVAILABLE, STATE_UNKNOWN]:
-                if state.state == STATE_UNAVAILABLE:
-                    self._attr_available = False
-            else:
-                try:
-                    self._state = Decimal(state.state)
-                except (DecimalException, ValueError) as err:
-                    _LOGGER.warning(
-                        "%s could not restore last state %s: %s",
-                        self.entity_id,
-                        state.state,
-                        err,
-                    )
-
-            self._attr_device_class = state.attributes.get(ATTR_DEVICE_CLASS)
-            self._unit_of_measurement = state.attributes.get(ATTR_UNIT_OF_MEASUREMENT)
 
         if self._max_sub_interval is not None:
             source_state = self.hass.states.get(self._sensor_source_id)
diff --git a/tests/components/integration/test_sensor.py b/tests/components/integration/test_sensor.py
index 500d567dca4..1a729f6254e 100644
--- a/tests/components/integration/test_sensor.py
+++ b/tests/components/integration/test_sensor.py
@@ -30,7 +30,6 @@ import homeassistant.util.dt as dt_util
 from tests.common import (
     MockConfigEntry,
     async_fire_time_changed,
-    mock_restore_cache,
     mock_restore_cache_with_extra_data,
 )
 
@@ -146,42 +145,6 @@ async def test_state(hass: HomeAssistant, method) -> None:
 
 
 async def test_restore_state(hass: HomeAssistant) -> None:
-    """Test integration sensor state is restored correctly."""
-    mock_restore_cache(
-        hass,
-        (
-            State(
-                "sensor.integration",
-                "100.0",
-                {
-                    "device_class": SensorDeviceClass.ENERGY,
-                    "unit_of_measurement": UnitOfEnergy.KILO_WATT_HOUR,
-                },
-            ),
-        ),
-    )
-
-    config = {
-        "sensor": {
-            "platform": "integration",
-            "name": "integration",
-            "source": "sensor.power",
-            "round": 2,
-        }
-    }
-
-    assert await async_setup_component(hass, "sensor", config)
-    await hass.async_block_till_done()
-
-    state = hass.states.get("sensor.integration")
-    assert state
-    assert state.state == "100.00"
-    assert state.attributes.get("unit_of_measurement") == UnitOfEnergy.KILO_WATT_HOUR
-    assert state.attributes.get("device_class") == SensorDeviceClass.ENERGY
-    assert state.attributes.get("last_good_state") is None
-
-
-async def test_restore_unavailable_state(hass: HomeAssistant) -> None:
     """Test integration sensor state is restored correctly."""
     mock_restore_cache_with_extra_data(
         hass,
@@ -237,9 +200,7 @@ async def test_restore_unavailable_state(hass: HomeAssistant) -> None:
         },
     ],
 )
-async def test_restore_unavailable_state_failed(
-    hass: HomeAssistant, extra_attributes
-) -> None:
+async def test_restore_state_failed(hass: HomeAssistant, extra_attributes) -> None:
     """Test integration sensor state is restored correctly."""
     mock_restore_cache_with_extra_data(
         hass,
@@ -271,42 +232,7 @@ async def test_restore_unavailable_state_failed(
 
     state = hass.states.get("sensor.integration")
     assert state
-    assert state.state == STATE_UNAVAILABLE
-
-
-async def test_restore_state_failed(hass: HomeAssistant) -> None:
-    """Test integration sensor state is restored correctly."""
-    mock_restore_cache(
-        hass,
-        (
-            State(
-                "sensor.integration",
-                "INVALID",
-                {
-                    "last_reset": "2019-10-06T21:00:00.000000",
-                },
-            ),
-        ),
-    )
-
-    config = {
-        "sensor": {
-            "platform": "integration",
-            "name": "integration",
-            "source": "sensor.power",
-        }
-    }
-
-    assert await async_setup_component(hass, "sensor", config)
-    await hass.async_block_till_done()
-
-    state = hass.states.get("sensor.integration")
-    assert state
-    assert state.state == "unknown"
-    assert state.attributes.get("unit_of_measurement") is None
-    assert state.attributes.get("state_class") is SensorStateClass.TOTAL
-
-    assert "device_class" not in state.attributes
+    assert state.state == STATE_UNKNOWN
 
 
 async def test_trapezoidal(hass: HomeAssistant) -> None: