diff --git a/homeassistant/components/integration/sensor.py b/homeassistant/components/integration/sensor.py
index ef587e405e6..ed017a21527 100644
--- a/homeassistant/components/integration/sensor.py
+++ b/homeassistant/components/integration/sensor.py
@@ -30,7 +30,6 @@ from homeassistant.const import (
 )
 from homeassistant.core import Event, HomeAssistant, State, callback
 from homeassistant.helpers import (
-    condition,
     config_validation as cv,
     device_registry as dr,
     entity_registry as er,
@@ -97,57 +96,72 @@ class _IntegrationMethod(ABC):
         return _NAME_TO_INTEGRATION_METHOD[method_name]()
 
     @abstractmethod
-    def validate_states(self, left: State, right: State) -> bool:
+    def validate_states(
+        self, left: State, right: State
+    ) -> tuple[Decimal, Decimal] | None:
         """Check state requirements for integration."""
 
     @abstractmethod
     def calculate_area_with_two_states(
-        self, elapsed_time: float, left: State, right: State
+        self, elapsed_time: Decimal, left: Decimal, right: Decimal
     ) -> Decimal:
         """Calculate area given two states."""
 
     def calculate_area_with_one_state(
-        self, elapsed_time: float, constant_state: State
+        self, elapsed_time: Decimal, constant_state: Decimal
     ) -> Decimal:
-        return Decimal(constant_state.state) * Decimal(elapsed_time)
+        return constant_state * elapsed_time
 
 
 class _Trapezoidal(_IntegrationMethod):
     def calculate_area_with_two_states(
-        self, elapsed_time: float, left: State, right: State
+        self, elapsed_time: Decimal, left: Decimal, right: Decimal
     ) -> Decimal:
-        return Decimal(elapsed_time) * (Decimal(left.state) + Decimal(right.state)) / 2
+        return elapsed_time * (left + right) / 2
 
-    def validate_states(self, left: State, right: State) -> bool:
-        return _is_numeric_state(left) and _is_numeric_state(right)
+    def validate_states(
+        self, left: State, right: State
+    ) -> tuple[Decimal, Decimal] | None:
+        if (left_dec := _decimal_state(left.state)) is None or (
+            right_dec := _decimal_state(right.state)
+        ) is None:
+            return None
+        return (left_dec, right_dec)
 
 
 class _Left(_IntegrationMethod):
     def calculate_area_with_two_states(
-        self, elapsed_time: float, left: State, right: State
+        self, elapsed_time: Decimal, left: Decimal, right: Decimal
     ) -> Decimal:
         return self.calculate_area_with_one_state(elapsed_time, left)
 
-    def validate_states(self, left: State, right: State) -> bool:
-        return _is_numeric_state(left)
+    def validate_states(
+        self, left: State, right: State
+    ) -> tuple[Decimal, Decimal] | None:
+        if (left_dec := _decimal_state(left.state)) is None:
+            return None
+        return (left_dec, left_dec)
 
 
 class _Right(_IntegrationMethod):
     def calculate_area_with_two_states(
-        self, elapsed_time: float, left: State, right: State
+        self, elapsed_time: Decimal, left: Decimal, right: Decimal
     ) -> Decimal:
         return self.calculate_area_with_one_state(elapsed_time, right)
 
-    def validate_states(self, left: State, right: State) -> bool:
-        return _is_numeric_state(right)
+    def validate_states(
+        self, left: State, right: State
+    ) -> tuple[Decimal, Decimal] | None:
+        if (right_dec := _decimal_state(right.state)) is None:
+            return None
+        return (right_dec, right_dec)
 
 
-def _is_numeric_state(state: State) -> bool:
+def _decimal_state(state: str) -> Decimal | None:
     try:
-        float(state.state)
-    except (ValueError, TypeError):
-        return False
-    return True
+        return Decimal(state)
+    except (InvalidOperation, TypeError):
+        return None
 
 
 _NAME_TO_INTEGRATION_METHOD: dict[str, type[_IntegrationMethod]] = {
@@ -413,7 +427,7 @@ class IntegrationSensor(RestoreSensor):
         if old_state is None or new_state is None:
             return
 
-        if condition.state(self.hass, new_state, [STATE_UNAVAILABLE]):
+        if new_state.state == STATE_UNAVAILABLE:
             self._attr_available = False
             self.async_write_ha_state()
             return
@@ -421,18 +435,16 @@ class IntegrationSensor(RestoreSensor):
         self._attr_available = True
         self._derive_and_set_attributes_from_state(new_state)
 
-        if not self._method.validate_states(old_state, new_state):
+        if not (states := self._method.validate_states(old_state, new_state)):
             self.async_write_ha_state()
             return
 
-        elapsed_seconds = (
-            new_state.last_updated - old_state.last_updated
-        ).total_seconds()
-
-        area = self._method.calculate_area_with_two_states(
-            elapsed_seconds, old_state, new_state
+        elapsed_seconds = Decimal(
+            (new_state.last_updated - old_state.last_updated).total_seconds()
         )
 
+        area = self._method.calculate_area_with_two_states(elapsed_seconds, *states)
+
         self._update_integral(area)
         self.async_write_ha_state()
 
diff --git a/tests/components/integration/test_sensor.py b/tests/components/integration/test_sensor.py
index 53763247bdf..555cb44caf5 100644
--- a/tests/components/integration/test_sensor.py
+++ b/tests/components/integration/test_sensor.py
@@ -629,8 +629,17 @@ async def test_device_class(hass: HomeAssistant, method) -> None:
     assert state.attributes.get("device_class") == SensorDeviceClass.ENERGY
 
 
-@pytest.mark.parametrize("method", ["trapezoidal", "left", "right"])
-async def test_calc_errors(hass: HomeAssistant, method) -> None:
+@pytest.mark.parametrize(
+    ("method", "expected_states"),
+    [
+        ("trapezoidal", [STATE_UNKNOWN, "0.500", "0.500"]),
+        ("left", [STATE_UNKNOWN, "0.000", "1.000"]),
+        ("right", ["0.000", "1.000", "1.000"]),
+    ],
+)
+async def test_calc_errors(
+    hass: HomeAssistant, method: str, expected_states: list[str]
+) -> None:
     """Test integration sensor units using a power source."""
     config = {
         "sensor": {
@@ -649,9 +658,9 @@ async def test_calc_errors(hass: HomeAssistant, method) -> None:
     hass.states.async_set(entity_id, None, {})
     await hass.async_block_till_done()
 
-    state = hass.states.get("sensor.integration")
     # With the source sensor in a None state, the Reimann sensor should be
     # unknown
+    state = hass.states.get("sensor.integration")
     assert state is not None
     assert state.state == STATE_UNKNOWN
 
@@ -665,7 +674,7 @@ async def test_calc_errors(hass: HomeAssistant, method) -> None:
 
     state = hass.states.get("sensor.integration")
     assert state is not None
-    assert state.state == STATE_UNKNOWN if method != "right" else "0.000"
+    assert state.state == expected_states[0]
 
     # With the source sensor updated successfully, the Reimann sensor
     # should have a zero (known) value.
@@ -677,7 +686,18 @@ async def test_calc_errors(hass: HomeAssistant, method) -> None:
 
     state = hass.states.get("sensor.integration")
     assert state is not None
-    assert round(float(state.state)) == 0 if method != "right" else 1
+    assert state.state == expected_states[1]
+
+    # Set the source sensor back to a non numeric state
+    now += timedelta(seconds=3600)
+    with freeze_time(now):
+        hass.states.async_set(entity_id, "unexpected", {"device_class": None})
+        await hass.async_block_till_done()
+    await hass.async_block_till_done()
+
+    state = hass.states.get("sensor.integration")
+    assert state is not None
+    assert state.state == expected_states[2]
 
 
 async def test_device_id(