Template Sensor

The template platform supports sensors which get their values from other entities.

Configuration

The configuration of Template Sensors depends on what you want them to be. Adding the following to your configuration.yaml file will create two sensors, one for the current sun angle and one for the time of the next sunrise:

# Example configuration.yaml entry
sensor:
  - platform: template
    sensors:
      solar_angle:
        friendly_name: "Sun angle"
        unit_of_measurement: 'degrees'
        value_template: "{{ state_attr('sun.sun', 'elevation') }}"

      sunrise:
        value_template: "{{ state_attr('sun.sun', 'next_rising') }}"

Considerations

Startup

If you are using the state of a platform that takes extra time to load, the Template Sensor may get an unknown state during startup. To avoid this (and the resulting error messages in your log file), you can use is_state() function in your template. For example, you would replace {{ states.cover.source.state == 'open' }} with this equivalent that returns true/false and never gives an unknown result:

{{ is_state('switch.source', 'on') }}

Entity IDs

The template engine will attempt to work out what entities should trigger an update of the sensor. This can fail, for example, if your template loops over the contents of a group. In this case, you can use entity_id to provide a list of entity IDs that will cause the sensor to update or you can run the service homeassistant.update_entity to update the sensor at will.

Examples

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

Sun Angle

This example shows the sun angle in the frontend.

sensor:
  - platform: template
    sensors:
      solar_angle:
        friendly_name: "Sun Angle"
        unit_of_measurement: '°'
        value_template: "{{ '%+.1f'|format(state_attr('sun.sun', 'elevation')) }}"

Renaming Sensor Output

If you don’t like the wording of a sensor output, then the Template Sensor can help too. Let’s rename the output of the Sun component as a simple example:

sensor:
  - platform: template
    sensors:
      sun_state:
        friendly_name: "Sun State"
        value_template: >-
          {% if is_state('sun.sun', 'above_horizon') %}
            up
          {% else %}
            down
          {% endif %}

Multiline Example With an if Test

This example shows a multiple line template with an if test. It looks at a sensing switch and shows on/off in the frontend.

sensor:
  - platform: template
    sensors:
      kettle:
        friendly_name: "Kettle"
        value_template: >-
          {% if is_state('switch.kettle', 'off') %}
            off
          {% elif state_attr('switch.kettle', 'kwh')|float < 1000 %}
            standby
          {% elif is_state('switch.kettle', 'on') %}
            on
          {% else %}
            failed
          {% endif %}

Change The Unit of Measurement

With a Template Sensor, it’s easy to convert given values into others if the unit of measurement doesn’t fit your needs.

sensor:
  - platform: template
    sensors:
      transmission_down_speed_kbps:
        friendly_name: "Transmission Down Speed"
        unit_of_measurement: 'kB/s'
        value_template: "{{ states('sensor.transmission_down_speed')|float * 1024 }}"

      transmission_up_speed_kbps:
        friendly_name: "Transmission Up Speed"
        unit_of_measurement: 'kB/s'
        value_template: "{{ states('sensor.transmission_up_speed')|float * 1024 }}"

Change The Icon

This example shows how to change the icon based on the day/night cycle.

sensor:
  - platform: template
    sensors:
      day_night:
        friendly_name: "Day/Night"
        value_template: >-
          {% if is_state('sun.sun', 'above_horizon') %}
            Day
          {% else %}
            Night
          {% endif %}
        icon_template: >-
          {% if is_state('sun.sun', 'above_horizon') %}
            mdi:weather-sunny
          {% else %}
            mdi:weather-night
          {% endif %}

Change The Entity Picture

This example shows how to change the entity picture based on the day/night cycle.

sensor:
  - platform: template
    sensors:
      day_night:
        friendly_name: "Day/Night"
        value_template: >-
          {% if is_state('sun.sun', 'above_horizon') %}
            Day
          {% else %}
            Night
          {% endif %}
        entity_picture_template: >-
          {% if is_state('sun.sun', 'above_horizon') %}
            /local/daytime.png
          {% else %}
            /local/nighttime.png
          {% endif %}

Change the Friendly Name Used in the Frontend

This example shows how to change the friendly_name based on a state.

sensor:
  - platform: template
    sensors:
      net_power:
        friendly_name_template: >-
          {% if states('sensor.power_consumption')|float < 0 %}
            Power Consumption
          {% else %}
            Power Production
          {% endif %}
        value_template: "{{ states('sensor.power_consumption') }}"
        unit_of_measurement: 'kW'

Add Custom Attributes

This example shows how to add custom attributes.

sensor:
  - platform: template
    sensors:
      my_device:
        value_template: >-
          {% if is_state('device_tracker.my_device_nmap','home') %}
            Home
          {% else %}
            {{ states('device_tracker.my_device_gps') }}
          {% endif %}
        attribute_templates:
          latitude: >-
            {% if is_state('device_tracker.my_device_nmap','home') %}
              {{ state_attr('zone.home','latitude') }}
            {% else %}
              state_attr('device_tracker.my_device_gps','latitude')
            {% endif %}
          longitude: >-
            {% if is_state('device_tracker.my_device_nmap','home') %}
              {{ state_attr('zone.home','longitude') }}
            {% else %}
              {{ state_attr('device_tracker.my_device_gps','longitude') }}
            {% endif %}

Working without entities

The template sensors are not limited to use attributes from other entities but can also work with Home Assistant’s template extensions.

This template contains no entities that will trigger an update (as now() is a function), so we add an entity_id: line with an entity that will force an update - here we’re using a date sensor to get a daily update:

sensor:
  - platform: template
    sensors:
      nonsmoker:
        value_template: "{{ (( as_timestamp(now()) - as_timestamp(strptime('06.07.2018', '%d.%m.%Y')) ) / 86400 ) | round(2) }}"
        entity_id: sensor.date
        friendly_name: 'Not smoking'
        unit_of_measurement: "Days"

In this case it is also possible to convert the entity-less template above into one that will be updated automatically:

sensor:
  - platform: template
    sensors:
      nonsmoker:
        value_template: "{{ (( as_timestamp(strptime(states('sensor.date'), '%Y-%m-%d')) - as_timestamp(strptime('06.07.2018', '%d.%m.%Y')) ) / 86400 ) | round(2) }}"
        friendly_name: 'Not smoking'
        unit_of_measurement: "Days"

Useful entities to choose might be sensor.date which update once per day or sensor.time, which updates once per minute.
Please note that the resulting template will be evaluated by Home Assistant state engine on every state change of these sensors, which in case of sensor.time happens every minute and might have a negative impact on performance.

An alternative to this is to create an interval-based automation that calls the service homeassistant.update_entity for the entities requiring updates. This modified example updates every 5 minutes:

sensor:
  - platform: template
    sensors:
      nonsmoker:
        value_template: "{{ (( as_timestamp(now()) - as_timestamp(strptime('06.07.2018', '%d.%m.%Y')) ) / 86400 ) | round(2) }}"
        entity_id: []
        friendly_name: 'Not smoking'
        unit_of_measurement: "Days"

automation:
  - alias: 'nonsmoker_update'
    trigger:
      - platform: time_pattern
        minutes: '/5'
    action:
      - service: homeassistant.update_entity
        entity_id: sensor.nonsmoker