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Water heater entities now expose their temperature unit

· 2 min read
Erik Montnemery

As of Home Assistant Core 2026.11, water heater entities have a new temperature_unit state attribute, and the temperature properties integrations implement have been renamed with a native_ prefix.

Background​

The water heater entity converts all temperatures it writes to the state machine to the unit system configured by the user. Until now, the unit was not part of the state, so anyone reading the state had to know that water heater temperatures follow the configured unit system. This is inconsistent with other entities, such as sensor, number and weather, which expose the unit next to the value.

The temperature_unit state attribute​

The temperature_unit state attribute holds the unit of the temperatures in the state, which is the temperature unit of the user's configured unit system. It's set by the WaterHeaterEntity base class and can't be overridden by integrations.

Renamed properties​

Integrations specify temperatures in the unit used by the device, and the base class converts them. To make that clear, and to match how sensor, number and weather entities name native values, the following properties and their _attr_ shorthand attributes have been renamed:

Old nameNew name
current_temperaturenative_current_temperature
target_temperaturenative_target_temperature
target_temperature_highnative_target_temperature_high
target_temperature_lownative_target_temperature_low
temperature_unitnative_temperature_unit

The old names keep working, but implementing them, setting the _attr_ attributes or reading them logs a warning. Support for the old names will be removed in Home Assistant Core 2027.11.

min_temp, max_temp and target_temperature_step are not renamed, and are still specified in the native unit.

More details can be found in the water heater entity documentation.

Example​

Old:

class MyWaterHeaterEntity(WaterHeaterEntity):
    _attr_temperature_unit = UnitOfTemperature.CELSIUS

    @property
    def current_temperature(self) -> float | None:
        return self.device.temperature

    async def async_update(self) -> None:
        self._attr_target_temperature = await self.device.get_setpoint()

New:

class MyWaterHeaterEntity(WaterHeaterEntity):
    _attr_native_temperature_unit = UnitOfTemperature.CELSIUS

    @property
    def native_current_temperature(self) -> float | None:
        return self.device.temperature

    async def async_update(self) -> None:
        self._attr_native_target_temperature = await self.device.get_setpoint()