Set `last_reset` attribute if energy monitor reset value

Configuration
1

Hello,
I have sensor.corridor_energy_monitor_total sensor who display kWh.
I create template sensor with last_reset attribute :

template:
  - sensor:
      - unique_id: energy_monitor_total2
        name: "energy_monitor_total"
        unit_of_measurement: 'kWh'
        state: >
          {{ (states("sensor.corridor_energy_monitor_total") | float) | round(2) }}       
        device_class: energy
        state_class: measurement
        attributes:
          last_reset: >
            {%- if states('sensor.corridor_energy_monitor_total') < states('sensor.energy_monitor_total2') -%}
              {{ now() }}
            {%- else -%}
              {{ '1970-01-01T00:00:00+00:00' }} # or last state of this attribute if exists
            {%- endif -%}

I want to set last value of this attribute or default value (‘1970-01-01T00:00:00+00:00’) if not exists last value in ‘else’ condition.

How can I do it?

1 Like
2

The measurement state class does not require a last_reset attribute.

See: Sensor Entity | Home Assistant Developer Docs

Also you are just copying the state of another sensor. This is not required either. You can add attributes to the original sensor using customize.

I’d suggest:

homeassistant:
  customize:
    sensor.corridor_energy_monitor_total:
      device_class: energy
      state_class: total_increasing
3

It not resolve my problem, because I want to change last_reset attribute if sensor.corridor_energy_monitor_total sensor reset its value.

4

And as I said:

5

I know, but last_reset attribute is required by Energy dashboard. I want to use Energy dashboard with my custom sensor.

6

Nope.

That is only required for a sensor with a state_class of total_increasing. Even then it is updated automatically for you.

If your sensor periodically resets the energy dashboard will take care of this for you if your sensor has the attributes:

      device_class: energy
      state_class: total_increasing

As long as sensor.corridor_energy_monitor_total has those two attributes, and an appropriate unit_of_measurement (Wh or kWh), you can use it with the energy dashboard.

7

Tnx for information.

I have one more question:
Is it a problem if my sensor resets value at different periods?

8

Nope. The energy dashboard will recognise a decrease in value as a reset at any time.

An issue only occurs if your sensor goes to 0 when unavailable then reverts to the full previous total. Then that whole total gets added to the recorded energy. This happens a lot with poorly constructed template sensors. e.g.

value → 0 → value : add the whole value to the energy total

value → unknown → value : add nothing to the total.

So if your energy sensor starts climbing up normally after resetting to zero it will work fine.