With the help of Home-Assistant templates, data from various sensors can be converted, combined or provided with your own formulas. Templates allow the creation of logic blocks for use in custom sensors, conditions or for customizing specific values in Lovelance Cards. The syntax used is Jinja2, a fully functional template engine for Python.

Where can templates be used?

Templates can be used in the following Home Assistant components:

• Developer tools / TEMPLATE
• Template sensors (under Helpers)
• automations
• certain Lovelance Cards

Developer tools

If you want to create a new sensor based on a template, you can do this in the settings under "Devices & services", "CREATE HELPER" and "Template":

Template sensor: Helper

Originally, template-sensors were stored in the configuration.yaml file. In current Home Assistant versions, the templates can be conveniently created as helpers in the Home Assistant interface. The helpers already show the calculated values or any syntax errors when they are created.

Menu item: Settings, Create helper -> Template:

You can select the options for a binary sensor, i.e. "On" and "Off", or any other sensor:

To create, see on this page: Template examples

Automations

The template sensors created could be used in an automation, or alternatively they offer the option of storing a template block directly in the triggers or conditions:

Within the automations, templates can be used as triggers, conditions and in the conditions of actions:

See also: Home Assistant automation - possibilities & basics

Template examples

To interpret the values of certain sensors or variables, these can be written in Jinja2 within {{ and }}. Variables can be set using the following syntax: {% set variable = 1 %}. "if", "else", or "else if" statements can also be interpreted within {% and %}. Comments can be added within {# and #}.

As a concrete example of a template sensor, the time could be made available as a separate entity from the date and time for the next sunrise. The integrated sensor for the sunrise is available in the following format: 2023-09-12T07:40:21.796007+00:00. The following template can be used to extract the time:

{{
as_timestamp(states.sun.sun.attributes.next_rising) | 
timestamp_custom('%H:%M')
}}

"as_timestamp" thereby converts the value ("states.") of the sensor "sun.sun.attributes.next_rising" into a Unix timestamp. A pipe "|" to the function "timestamp_custom" converts the timestamp back into "hours": "minutes": '%H:%M'. As already mentioned, the template can be tested in the developer tools:

Used as a template sensor, this also shows a preview of the result:

When the template sensor is saved, a new sensor with the ID: sensor.name, in this case "sensor.sunrise", is created and is available as a separate entity in Home Assistant. For more information on template sensors and their unit of measurement, device and status class, see the following page: Home Assistant Sensors - Basics

Template - Cheat Sheet

Here are a few sample templates:

{{ as_timestamp(states.sun.sun.attributes.next_rising) | timestamp_custom(' %H:%M') | replace(" 0", "") }}

 {{ as_timestamp(states.sun.sun.attributes.next_setting) | timestamp_custom(' %H:%M') | replace(" 0", "") }}

 {{ as_timestamp(states.sun.sun.attributes.next_rising) | timestamp_custom(' %H:%M') | replace(" 0", "") }} -
 {{ as_timestamp(states.sun.sun.attributes.next_setting) | timestamp_custom(' %H:%M') | replace(" 0", "") }}

{{ as_timestamp(states.sun.sun.attributes.next_rising) | timestamp_custom(' %H:%M') | replace(" 0", "") }} - 
{{ as_timestamp(states.sun.sun.attributes.next_setting) | timestamp_custom(' %H:%M') | replace(" 0", "") }}

{{ as_timestamp(now()) | timestamp_custom('%H%M') | float  > (states.sun.sun.attributes.next_rising |as_timestamp) | timestamp_custom("%H%M", True) | float }}

{{ as_timestamp(now() - timedelta(minutes=180))  | timestamp_custom('%H%M') | float  > (states.sun.sun.attributes.next_rising |as_timestamp) | timestamp_custom("%H%M", True) | float}}

{{ as_timestamp(now()) | timestamp_custom('%H%M') | float  > (states.sun.sun.attributes.next_setting |as_timestamp) | timestamp_custom("%H%M", True) | float }}

{% set now = (as_timestamp(now()) | timestamp_custom('%H:%M')) %}
{% set sr = (as_timestamp(states.sun.sun.attributes.next_rising) | timestamp_custom('%H:%M')) %}  
{% set ss = (as_timestamp(states.sun.sun.attributes.next_setting) | timestamp_custom('%H:%M')) %} 
{% set start = now if now > sr else sr %}
{% if now < ss %}
{{ (((ss.split(":")[0] | int * 60 + ss.split(":")[1] | int) - (start.split(":")[0] | int * 60 + start.split(":")[1] | int)) / 60) | round(2) }}
{% else %}
0
{% endif %}

{% set V = states('sensor.meter01_voltage_l1') | float %}
{% set A = states('sensor.meter01_current_l1') | float %}
{{ ( 0.9 * A * V) | round(0)}}

{% set value = states('sensor.heating_active_power') | float %}
          {{ "off" if value < 10 else 
          "pump" if value < 58 else 
          "water" if value < 70 else 
          "pump" if value < 125 else 
          "heat" }}

{{ (((as_timestamp(now()) - 
as_timestamp(states.switch.relay_heizung_puffer_kalt.last_changed)) / 60) | int) 
  > 30 }} 

{% set pumpen = states('sensor.heizung_pumpe_eg_active_power') | float if states('sensor.heizung_pumpe_eg_active_power') | is_number else 0   %}

Use previous value in template sensor

Using the following template, a template sensor (here sensor.lastavailablestate) can return the last value that was not "unavailable":

{% if states('sensor.sometimes_unavailable')  != 'unavailable'%}
    {{ sensor.sometimes_unavailable }}
{% else %}
    {{ states('sensor.lastavailablestate') }}
{% endif %}