Template sensor to return last available sensor value

Configuration
1

I need a sensor to show the last available value of a sensor so that when the sensor is not available I can display the last value;

So far, I have this, but it shows ‘unknown’ when the sensor is not available.

{% if states('sensor.458_battery_monitor') != 'unavailable' %}
  {{ states('sensor.458_battery_monitor) }}
{% else %}
  {{ states('sensor.battery_voltage_backup') | default(states('sensor.458_battery_monitor').last_updated_value) }}
{% endif %}

When the sensor is available it returns the current value OK.

How ca I access the last value of the sensor from the recorder, I assume, to use in the template sensor?

Any ideas? Is this possible?

2 
{% if has_value('sensor.458_battery_monitor') %}
  {{ states('sensor.458_battery_monitor') }}
{% else %}
  {{ this.state }}
{% endif %}

if you want it to persist over restarts you have to make a trigger based template entity.

  - trigger:
      - trigger: state
        entity_id: sensor.458_battery_monitor
        not_to:
          - unknown
          - unavailable
    sensor:
      - name: 458_battery_monitor 2
        state: '{{ trigger.to_state.state }}'
3

Thank you, Petro.

I’ve tried this but get the error “‘this’ is undefined”.

What is ‘this.state’?

I’m assuming that the below is a storage of the most recent value.

  - trigger:
      - trigger: state
        entity_id: sensor.458_battery_monitor
        not_to:
          - unknown
          - unavailable
    sensor:
      - name: 458_battery_monitor 2
        state: '{{ trigger.to_state.state }}'

In which case I just change {{ this.state }} to {{ 458_battery_monitor 2.state }}.

Is that correct?

4

that won’t work in the template editor, only in your entity. this.state is the current state.

it’s just an entity that represents the latest state that is available.

5

Here’s where I’m at, but the created sensors aren’t available. I have reloaded the template entities. Does it need a full restart?

- sensor:
    - name:
      unique_id: stored_458_battery_voltage
      state: >
        {% if has_value('sensor.458_battery_monitor') %}
          {{ states('sensor.458_battery_monitor') }}
        {% else %}
          {{ sensor.458_battery_monitor_voltage_store }}
        {% endif %}

- template:
    - trigger:
        - trigger: state
          entity_id: sensor.458_battery_monitor_458_battery_voltage
          not_to:
            - unknown
            - unavailable
      sensor:
        - name: 458_battery_monitor_voltage_store
          state: "{{ trigger.to_state.state }}"
6 
- sensor:
    - name:
      unique_id: stored_458_battery_voltage
      state: >
        {% if has_value('sensor.458_battery_monitor') %}
          {{ states('sensor.458_battery_monitor') }}
        {% else %}
          {{ this.state }}
        {% endif %}
- trigger:
    - trigger: state
      entity_id: sensor.458_battery_monitor_458_battery_voltage
      not_to:
        - unknown
        - unavailable
  sensor:
    - name: 458_battery_monitor_voltage_store
      state: "{{ trigger.to_state.state }}"
7

Brilliant!

Thank you for your help and time. I appreciate it.

8

I have a very similar issue, but I don’t understand how can I apply to an automation without creating a new sensor. I think it should be very simple to get the last valid value of a sensor… But it isn’t!
this is what I did:

alias: Svuotamento Serbatoio
description: ""
triggers:
  - trigger: state
    entity_id:
      - sensor.esymini_troiano_fct_total_delivered_flow_mc
    not_to:
      - unknown
      - unavailable
conditions: []
actions:
  - action: input_number.set_value
    target:
      entity_id: input_number.livello_serbatoio
    data:
      value: >-
        {{ max(states('input_number.livello_serbatoio') |
        float(states('input_number.capacita_massima_serbatoio') | int) -  (
        trigger.to_state.state | float - trigger.from_state.state | float ) *
        1000, 0) | round(2) }}
  - action: automation.turn_on
    metadata: {}
    data: {}
    target:
      entity_id: automation.riempimento_serbatoio
mode: single

I would manage the case where trigger.from_state is not available giving a “default” value in float(default) where default should be the last sensor valid value.
Is it possible?

9

Look carefully! The solution from @petro was not an automation, even though it has triggers. It is a trigger-based sensor template.

10

Yes I saw, but I want to get the last valid value inside the automation without creating a duplicate sensor of the original only to fix the unavailable states.

11

Creating a new sensor for that purpose is the most straightforward way to go about it on the Home Assistant platform, even if it feels like there should be a more minimalist way.

There is not, to my knowledge, a way to access prior states of a sensor from within a script or automation, at least not without introducing major new headaches that would dwarf the inconvenience of a new sensor.

12

My card reads from abstract_weight, but after a HA reboot, it shows up as NaN until I step on the weighing machine again.

I tried the trigger, but wasn’t able to get it to work, can help me with this please? Thank you.

template:
  - sensor:
    - name: abstract_weight
      unique_id: abstract_weight
      icon: mdi:scale-bathroom
      unit_of_measurement: kg
      device_class: weight
      state: >
        {% set weight = states('sensor.from_hardware') | float %}
        {{ weight if weight >= 50 else this.state }}
      availability: "{{ has_value('sensor.from_hardware') }}"