Support retrieving the last known value in templates for unavailable sensor entities

Feature Requests
1

There are tons of forum posts of people who also face this problem but it seems there is no nice solution to this: In my case, the entities of my PV inverter become unavailable once the device shuts down over night. The entities have a red exclamation mark next to them and all template sensors that use them (e.g. to calculate the daily yield of different systems) also show “unavailable”.
However, if I click on a respective entity I can see the last value and all previous values of the entity in its history.

image

It would be nice if one could use a filter or if there was a default attribute “last_value” populated for each sensor that could be used to avoid the above issues, i.e. to ensure that all other entities using this value still work.

2

Switch to a trigger-based template sensor using a State trigger set not to trigger on the “unavailable” state value.

3

Do you happen to have an example for how this could be done? I’ve been searching and I tried out different things but nothing works :confused:

4 
template:
  - trigger:
      - platform: state
        entity_id: sensor.symo_total_energy_example
        not_to:
          - unknown
          - unavailable
    sensor:
      - name: Symo Total Energy stable
        state: "{{ trigger.to_state.state }}"
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5

Thanks a lot - I will give it a try (I believe I have to wait until tomorrow / until the device turns on again for the sensor to contain a value).

6

There is, but you must use a template sensor to filter it.

template:
  - sensor:
      - name: Symo Total Energy stable
        device_class: energy
        state_class: total_increasing
        unit_of_measurement: kWh
        state: >
          {% if has_value('sensor.pv_energy') %}
            {{ states('sensor.pv_energy') }}
          {% else %}
            {{ this.state }}
          {% endif %}

Or in more compact form:

template:
  - sensor:
      - name: Symo Total Energy stable
        device_class: energy
        state_class: total_increasing
        unit_of_measurement: kWh
        state: "{{ states('sensor.pv_energy') if has_value('sensor.pv_energy') else this.state }}"

Or

template:
  - sensor:
      - name: Symo Total Energy stable
        device_class: energy
        state_class: total_increasing
        unit_of_measurement: kWh
        state: "{{ iif(has_value('sensor.pv_energy'), states('sensor.pv_energy'), this.state) }}"

EDIT: way too slow (I did not scroll down to see it had been answered already). Drew’s answer is another way using triggered template sensors.

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