Patform Template - how can I get previous state (its called from_state in actions)

Configuration
1

Hi guys,

switching from OH to HA. over the weekend. Steep learning curve behind me and ahead. I am really impressed by HA. One thing I am banging my head around for 6h now and i Need your help.

I have a sensor which gets every minute an update. Its a counter which counts 1/250 kWh and its just a number. I get it from KNX, but that should not matter.

With a sensor template I calculate this into kWh ( a number i can read and see on my meter).

- platform: template
  sensors:
    counter_power_kwh:
      friendly_name: "Strom"
      unit_of_measurement: 'kWh'
      value_template: >
        {{ (states("sensor.counter_power_impulse")|float - 16369685.0) / 250.0 + 35344.6 }}

I have another item which gets updated each time the above one gets updated. Target is to calculate delta kWh and delta T in seconds.

I checked in debugging. When I replace the from_state with a copy paste value from the previous run I get reasonable numbers (480W), however in HA I get 0.0 because from_state is always 0.0.

- platform: template
  sensors:
    counter_power_consumption:
      unit_of_measurement: 'W'
      value_template: >
        {% set delta_kWh = (states("sensor.counter_power_kwh")|float) - (states('states.sensor.counter_power_kwh.from_state')|float) %}
        {% set delta_s = (as_timestamp(now()) - as_timestamp(states.sensor.counter_power_kwh.last_changed)) %}
        {% if states('states.sensor.counter_power_kwh.from_state')|float == 0.0 %}
          0.0
        {% else %}
          {{ (delta_kWh / delta_s) * 1000.0 * 3600.0 }}
        {% endif %}

Can someone point me into the right direction? I have

  • an entity whith increasing kWh
  • I want a regular check how much kWh were consumed.
  • Say every 6min would be ok.It really does not matter how often.
  • with that delta kWh and delta T I can calculate the power consumption.
  • I need only delta from sensor (current and previous value).

How can I get this done? Is an automation the right way? How do I set a sensor item from an action?

I am stuck and need some sleep.

Thank you for reading so far.

Regards
Ralf

2

The derivative of energy is power. Unfortunately a derivative sensor has yet to be implemented. Add your vote here:

Until then the statistics sensor has change and change rate attributes you could use:

3

You could also perhaps use https://www.home-assistant.io/integrations/utility_meter/

to calculate changes and cumulative consumption.

You can configure watts into kWh in that sensor.

4

No you cant and he wants to go the other way anyway (kWh to W).

1 Like
5

Hello guys,

I am nearly there. I feel its 10minutes to HEUREKA. I am struggling with the last bit only which his using the service input_number.set_value to store the results which I now am able to calculate.

Short summary

  • I have a kWh meter which regularly announces its value
  • with the deltas between such two announcements one can calculate the power consumption
  • I want to store this value in an input_number. This stepp is missing.

This is the sensor which I have. It is set from actually a KNX sensor, but that should not matter.

[configuration.yaml]

sensors:
- platform: template
  sensors:
    counter_power_kwh:
      friendly_name: "Strom"
      unit_of_measurement: 'kWh'
      value_template: >
        {{ (states("sensor.counter_power_impulse")|float - 16369685.0) / 250.0 + 35344.6 }}

With the following action I calculate the delta in seconds and the delta in kWh between two announcements. With those I can calculate the power consumption.

[configuration.yaml]

automation:
- alias: counter_power_consumption
  trigger:
    - platform: state
      entity_id: sensor.counter_power_kwh
  action:
    - service: system_log.write
      data_template:
        level: error
        logger: homeassistant.components.mylogger
        # Upper bound 69 kW for a typic house is exceed when delta_kWh > 69.000 / 1.000 / 3.600 * (time between two updates)
        message: >-
          {% set delta_kWh = (trigger.to_state.state|float) - (trigger.from_state.state|float) %}
          {% set delta_s = (as_timestamp(now())|float - as_timestamp(states.automation.counter_power_consumption.attributes.last_triggered)|float) %}
          {% if trigger.from_state.state|float <= 0.0 or delta_s == 0.0 or delta_kWh > 69 / 3600 * 60 %}  
            "============== sensor mom verbrauch: NaN }}"
          {% else %}
            "============== sensor mom verbrauch: {{ (delta_kWh / delta_s) * 1000.0 * 3600.0  }}"
          {% endif %}

The trick to write int the logs helped tremendously to get this troubleshooted. Kudos.

The logs show useful numbers

============== sensor delta_s: 59.8812530040741
============== sensor delta_kwh: 0.007999999994353857
============== sensor mom verbrauch: 480.7244342533442

I miss the last step storing this into an input_number which is defined like this.

[configuration.yaml]

input_number:
  counter_power_consumption:
      name: Momentanverbrauch
      unit_of_measurement: "W"
      icon: mdi:gauge
      initial: 0.0
      min: 0.0
      max: 2000
      step: 20

I tried to add the following step into the action.

[configuration.yaml]

automation:
- alias: counter_power_consumption
  trigger:
    - platform: state
      entity_id: sensor.counter_power_kwh
  action:
    ... 
    - service: input_number.set_value
      data_template:
        entity_id: input_number.counter_power_consumption
        value: >-
          {% set delta_kWh = (trigger.to_state.state|float) - (trigger.from_state.state|float) %}
          {% set delta_s = (as_timestamp(now())|float - as_timestamp(states.automation.counter_power_consumption.attributes.last_triggered)|float) %}
          {% if trigger.from_state.state|float <= 0.0 or delta_s == 0.0 or delta_kWh > 69 / 3600 * 60 %}  
            0.0
          {% else %}
            {{ (delta_kWh / delta_s) * 1000.0 * 3600.0 }}
          {% endif %}

Above does not give an error message. However input_number.counter_power_consumptionstays at 0.

I added an additional step behind to prove that. In the gui I see 0 as well.

    - service: system_log.write
      data_template:
        level: error
        logger: homeassistant.components.mylogger
        message: "============== sensor mom verbrauch: {{ states.input_number.counter_power_consumption|float }}"

This one reports constantly.

============== sensor mom verbrauch: 0.0

What am I missing? How do I store a value in an input variable from an action?

I hope I can solve that soon with your help. I tried alone with little success.

Regards
Ralf

6

Looking in the log I get 0.0 output. But it seems actually working. I will report back tomorrow.