---
title: "MQTT water heater"
description: "Instructions on how to integrate MQTT water heater into Home Assistant."
ha_category:
  - Water heater
ha_release: 2023.7
ha_iot_class: Local Polling
ha_domain: mqtt
---

The `mqtt` water heater platform lets you control your MQTT enabled water heater devices.

## Configuration

To enable this water heater platform in your installation, first add the following to your `configuration.yaml` file:

```yaml
# Example configuration.yaml entry
mqtt:
  - water_heater:
      name: Boiler
      mode_command_topic: "basement/boiler/mode/set"
```

{% configuration %}
availability:
  description: A list of MQTT topics subscribed to receive availability (online/offline) updates. Must not be used together with `availability_topic`.
  required: false
  type: list
  keys:
    payload_available:
      description: The payload that represents the available state.
      required: false
      type: string
      default: online
    payload_not_available:
      description: The payload that represents the unavailable state.
      required: false
      type: string
      default: offline
    topic:
      description: An MQTT topic subscribed to receive availability (online/offline) updates.
      required: true
      type: string
    value_template:
      description: "Defines a [template](/docs/configuration/templating/#using-templates-with-the-mqtt-integration) to extract device's availability from the `topic`. To determine the devices's availability result of this template will be compared to `payload_available` and `payload_not_available`."
      required: false
      type: template
availability_mode:
  description: When `availability` is configured, this controls the conditions needed to set the entity to `available`. Valid entries are `all`, `any`, and `latest`. If set to `all`, `payload_available` must be received on all configured availability topics before the entity is marked as online. If set to `any`, `payload_available` must be received on at least one configured availability topic before the entity is marked as online. If set to `latest`, the last `payload_available` or `payload_not_available` received on any configured availability topic controls the availability.
  required: false
  type: string
  default: latest
availability_template:
  description: "Defines a [template](/docs/configuration/templating/#using-templates-with-the-mqtt-integration) to extract device's availability from the `availability_topic`. To determine the devices's availability result of this template will be compared to `payload_available` and `payload_not_available`."
  required: false
  type: template
availability_topic:
  description: The MQTT topic subscribed to receive availability (online/offline) updates. Must not be used together with `availability`.
  required: false
  type: string
current_temperature_template:
  description: A template with which the value received on `current_temperature_topic` will be rendered.
  required: false
  type: template
current_temperature_topic:
  description: The MQTT topic on which to listen for the current temperature. A `"None"` value received will reset the current temperature. Empty values (`'''`) will be ignored.
  required: false
  type: string
device:
  description: 'Information about the device this water heater device is a part of to tie it into the [device registry](https://developers.home-assistant.io/docs/en/device_registry_index.html). Only works through [MQTT discovery](/integrations/mqtt/#mqtt-discovery) and when [`unique_id`](#unique_id) is set. At least one of identifiers or connections must be present to identify the device.'
  required: false
  type: map
  keys:
    configuration_url:
      description: 'A link to the webpage that can manage the configuration of this device. Can be either an `http://`, `https://` or an internal `homeassistant://` URL.'
      required: false
      type: string
    connections:
      description: 'A list of connections of the device to the outside world as a list of tuples `[connection_type, connection_identifier]`. For example the MAC address of a network interface: `"connections": [["mac", "02:5b:26:a8:dc:12"]]`.'
      required: false
      type: list
    hw_version:
      description: The hardware version of the device.
      required: false
      type: string
    identifiers:
      description: 'A list of IDs that uniquely identify the device. For example a serial number.'
      required: false
      type: [list, string]
    manufacturer:
      description: 'The manufacturer of the device.'
      required: false
      type: string
    model:
      description: 'The model of the device.'
      required: false
      type: string
    name:
      description: 'The name of the device.'
      required: false
      type: string
    serial_number:
      description: "The serial number of the device."
      required: false
      type: string
    suggested_area:
      description: 'Suggest an area if the device isn’t in one yet.'
      required: false
      type: string
    sw_version:
      description: 'The firmware version of the device.'
      required: false
      type: string
    via_device:
      description: 'Identifier of a device that routes messages between this device and Home Assistant. Examples of such devices are hubs, or parent devices of a sub-device. This is used to show device topology in Home Assistant.'
      required: false
      type: string
enabled_by_default:
  description: Flag which defines if the entity should be enabled when first added.
  required: false
  type: boolean
  default: true
encoding:
  description: The encoding of the payloads received and published messages. Set to `""` to disable decoding of incoming payload.
  required: false
  type: string
  default: "utf-8"
entity_category:
  description: The [category](https://developers.home-assistant.io/docs/core/entity#generic-properties) of the entity.
  required: false
  type: string
initial:
  description: Set the initial target temperature. The default value depends on the temperature unit, and will be 43.3°C or 110°F.
  required: false
  type: integer
icon:
  description: "[Icon](/docs/configuration/customizing-devices/#icon) for the entity."
  required: false
  type: icon
json_attributes_template:
  description: "Defines a [template](/docs/configuration/templating/#using-templates-with-the-mqtt-integration) to extract the JSON dictionary from messages received on the `json_attributes_topic`. Usage example can be found in [MQTT sensor](/integrations/sensor.mqtt/#json-attributes-template-configuration) documentation."
  required: false
  type: template
json_attributes_topic:
  description: "The MQTT topic subscribed to receive a JSON dictionary payload and then set as sensor attributes. Usage example can be found in [MQTT sensor](/integrations/sensor.mqtt/#json-attributes-topic-configuration) documentation."
  required: false
  type: string
max_temp:
  description: Maximum set point available. The default value depends on the temperature unit, and will be 60°C or 140°F.
  type: float
  required: false
min_temp:
  description: Minimum set point available. The default value depends on the temperature unit, and will be 43.3°C or 110°F.
  type: float
  required: false
mode_command_template:
  description: A template to render the value sent to the `mode_command_topic` with.
  required: false
  type: template
mode_command_topic:
  description: The MQTT topic to publish commands to change the water heater operation mode.
  required: false
  type: string
mode_state_template:
  description: A template to render the value received on the `mode_state_topic` with.
  required: false
  type: template
mode_state_topic:
  description: The MQTT topic to subscribe for changes of the water heater operation mode. If this is not set, the operation mode works in optimistic mode (see below).
  required: false
  type: string
modes:
  description: A list of supported modes. Needs to be a subset of the default values.
  required: false
  default: ['off', 'eco', 'electric', 'gas', 'heat_pump', 'high_demand', 'performance']
  type: list
name:
  description: The name of the water heater. Can be set to `null` if only the device name is relevant.
  required: false
  type: string
  default: MQTT water heater
object_id:
  description: Used instead of `name` for automatic generation of `entity_id`
  required: false
  type: string
optimistic:
  description: Flag that defines if the water heater works in optimistic mode
  required: false
  type: boolean
  default: "`true` if no state topic defined, else `false`."
payload_available:
  description: The payload that represents the available state.
  required: false
  type: string
  default: online
payload_not_available:
  description: The payload that represents the unavailable state.
  required: false
  type: string
  default: offline
payload_off:
  description: The payload that represents disabled state.
  required: false
  type: string
  default: "OFF"
payload_on:
  description: The payload that represents enabled state.
  required: false
  type: string
  default: "ON"
power_command_template:
  description: A template to render the value sent to the `power_command_topic` with. The `value` parameter is the payload set for `payload_on` or `payload_off`.
  required: false
  type: template
power_command_topic:
  description: The MQTT topic to publish commands to change the water heater power state. Sends the payload configured with `payload_on` if the water heater is turned on via the `water_heater.turn_on`, or the payload configured with `payload_off` if the water heater is turned off via the `water_heater.turn_off` service. Note that `optimistic` mode is not supported through `water_heater.turn_on` and `water_heater.turn_off` services. When called, these services will send a power command to the device but will not optimistically update the state of the water heater. The water heater device should report its state back via `mode_state_topic`.
  required: false
  type: string
precision:
  description: The desired precision for this device. Can be used to match your actual water heater's precision. Supported values are `0.1`, `0.5` and `1.0`.
  required: false
  type: float
  default: 0.1 for Celsius and 1.0 for Fahrenheit.
qos:
  description: The maximum QoS level to be used when receiving and publishing messages.
  required: false
  type: integer
  default: 0
retain:
  description: Defines if published messages should have the retain flag set.
  required: false
  type: boolean
  default: false
temperature_command_template:
  description: A template to render the value sent to the `temperature_command_topic` with.
  required: false
  type: template
temperature_command_topic:
  description: The MQTT topic to publish commands to change the target temperature.
  required: false
  type: string
temperature_state_template:
  description: A template to render the value received on the `temperature_state_topic` with.
  required: false
  type: template
temperature_state_topic:
  description: The MQTT topic to subscribe for changes in the target temperature. If this is not set, the target temperature works in optimistic mode (see below). A `"None"` value received will reset the temperature set point. Empty values (`'''`) will be ignored.
  required: false
  type: string
temperature_unit:
  description: Defines the temperature unit of the device, `C` or `F`. If this is not set, the temperature unit is set to the system temperature unit.
  required: false
  type: string
unique_id:
   description: An ID that uniquely identifies this water heater device. If two water heater devices have the same unique ID, Home Assistant will raise an exception.
   required: false
   type: string
value_template:
  description: Default template to render the payloads on *all* `*_state_topic`s with.
  type: template
  required: false
{% endconfiguration %}

## Optimistic mode

If a property works in *optimistic mode* (when the corresponding state topic is not set), Home Assistant will assume that any state changes published to the command topics did work and change the internal state of the {% term entity %} immediately after publishing to the command topic. If it does not work in optimistic mode, the internal state of the {% term entity %} is only updated when the requested update is confirmed by the device through the state topic. You can enforce optimistic mode by setting the `optimistic` option to `true`. When set, the internal state will always be updated, even when a state topic is defined.

## Using templates

For all `*_state_topic`s, a template can be specified that will be used to render the incoming payloads on these topics. Also, a default template that applies to all state topics can be specified as `value_template`. This can be useful if you received payloads are e.g., in JSON format. Since in JSON, a quoted string (e.g., `"foo"`) is just a string, this can also be used for unquoting.

Say you receive the operation mode `"off"` via your `mode_state_topic`, but the mode is actually called just `off`, here's what you could do:

{% raw %}

```yaml
mqtt:
  - water_heater:
      name: Boiler
      modes:
        - "off"
        - "eco"
        - "performance"
      mode_command_topic: "basement/boiler/mode/set"
      mode_state_topic: "basement/boiler/mode/state"
      mode_state_template: "{{ value_json }}"
```

{% endraw %}

This will parse the incoming `"off"` as JSON, resulting in `off`. Obviously, in this case you could also just set `value_template: {% raw %}"{{ value_json }}"{% endraw %}`.

Similarly for `*_command_topic`s, a template can be specified to render the outgoing payloads on these topics.

## Example

A full configuration example looks like the one below.

{% raw %}

```yaml
# Full example configuration.yaml entry
mqtt:
  - water_heater:
      name: Boiler
      modes:
        - "off"
        - "eco"
        - "performance"
      mode_state_topic: "basement/boiler/mode"
      mode_command_topic: "basement/boiler/mode/set"
      mode_command_template: "{{ value if value=="off" else "on" }}"
      temperature_state_topic: "basement/boiler/temperature"
      temperature_command_topic: "basement/boiler/temperature/set"
      current_temperature_topic: "basement/boiler/current_temperature"
      precision: 1.0
```

{% endraw %}