MQTT Sensor

This mqtt sensor platform uses the MQTT message payload as the sensor value. If messages in this state_topic are published with RETAIN flag, the sensor will receive an instant update with last known value. Otherwise, the initial state will be undefined.


To use your MQTT sensor in your installation, add the following to your configuration.yaml file:

# Example configuration.yaml entry
  - platform: mqtt
    state_topic: "home/bedroom/temperature"

Configuration Variables


(string)(Required)The MQTT topic subscribed to receive sensor values.


(string)(Optional)Name of the MQTT sensor.

Default value: MQTT Sensor


(int)(Optional)The maximum QoS level of the state topic.

Default value: 0


(string)(Optional)Defines the units of measurement of the sensor, if any.


(string)(Optional)Icon for the sensor (e.g. mdi:gauge).


(int)(Optional)Defines the number of seconds after the value expires if it’s not updated.

Default value: 0


(template)(Optional)Defines a template to extract the value.


(boolean)Sends update events even if the value hasn’t changed. Useful if you want to have meaningful value graphs in history.

Default value: false


(string)(Optional)The MQTT topic subscribed to receive availability (online/offline) updates.


(string)(Optional)The payload that represents the available state.

Default value: online


(string)(Optional)The payload that represents the unavailable state.

Default value: offline


(list | string)A list of keys to extract values from a JSON dictionary payload and then set as sensor attributes.


(string)(Optional)An ID that uniquely identifies this sensor. If two sensors have the same unique ID, Home Assistant will raise an exception.


(device_class)(Optional)The type/class of the sensor to set the icon in the frontend.

Default value: None


In this section you find some real life examples of how to use this sensor.

JSON attributes configuration

The example sensor below shows a configuration example which uses JSON in the state topic to add extra attributes. It also makes use of the availability topic. Attributes can then be extracted in Templates. For example, to extract the ClientName attribute from the sensor below, use a template similar to: {{ state_attr('sensor.bs_rssi', 'ClientName') }}.

# Example configuration.yaml entry
  - platform: mqtt
    name: "BS RSSI"
    state_topic: "HUISHS/BunnyShed/NodeHealthJSON"
    unit_of_measurement: 'dBm'
    value_template: "{{ value_json.RSSI }}"
    availability_topic: "HUISHS/BunnyShed/status"
    payload_available: "online"
    payload_not_available: "offline"
      - ClientName
      - IP
      - MAC
      - RSSI
      - HostName
      - ConnectedSSID  

Get battery level

If you are using the OwnTracks and enable the reporting of the battery level then you can use a MQTT sensor to keep track of your battery. A regular MQTT message from OwnTracks looks like this:

owntracks/tablet/tablet {"_type":"location","lon":7.21,"t":"u","batt":92,"tst":144995643,"tid":"ta","acc":27,"lat":46.12}

Thus the trick is extracting the battery level from the payload.

# Example configuration.yaml entry
  - platform: mqtt
    name: "Battery Tablet"
    state_topic: "owntracks/tablet/tablet"
    unit_of_measurement: '%'
    value_template: "{{ value_json.batt }}"

Get temperature and humidity

If you are using a DHT sensor and a NodeMCU board (esp8266), you can retrieve temperature and humidity with a MQTT sensor. A code example can be found here. A regular MQTT message from this example looks like this:

    "temperature": 23.20,
    "humidity": 43.70

Then use this configuration example to extract the data from the payload:

# Example configuration.yaml entry
  - platform: mqtt
    name: "Temperature"
    state_topic: "office/sensor1"
    unit_of_measurement: '°C'
    value_template: "{{ value_json.temperature }}"
  - platform: mqtt
    name: "Humidity"
    state_topic: "office/sensor1"
    unit_of_measurement: '%'
    value_template: "{{ value_json.humidity }}"

Get sensor value from a device with ESPEasy

Assuming that you have flashed your ESP8266 unit with ESPEasy. Under “Config” set a name (“Unit Name:”) for your device (here it’s “bathroom”). A “Controller” for MQTT with the protocol “OpenHAB MQTT” is present and the entries (“Controller Subscribe:” and “Controller Publish:”) are adjusted to match your needs. In this example the topics are prefixed with “home”. Please keep in mind that the ESPEasy default topics start with a / and only contain the name when writing your entry for the configuration.yaml file.

  • Controller Subscribe: home/%sysname%/# (instead of /%sysname%/#)
  • Controller Publish: home/%sysname%/%tskname%/%valname% (instead of /%sysname%/%tskname%/%valname%)

Also, add a sensor in the “Devices” tap with the name “analog” and “brightness” as value.

As soon as the unit is online, you will get the state of the sensor.

home/bathroom/status Connected
home/bathroom/analog/brightness 290.00

The configuration will look like the example below:

# Example configuration.yaml entry
  - platform: mqtt
    name: "Brightness"
    state_topic: "home/bathroom/analog/brightness"