How to monitor a bad solar panel?

i have 13 panels. right now, the average is 19W as you can see.
how to set up an alert for a panel that is outputting less than 30% of all the average of 19w? so if inverter 993 is outputting 12w, i would get an alert instantly.

Create a min/max sensor that averages all your inverter powers. Name it PV Inverter Average Power

Notification automation:

Use a state trigger to trigger whenever any of the inverter powers change:

trigger:
  - platform: state
    entity_id:
      - sensor.invet_038
      - sensor.invet_164
      # list all the inverter power sensors here, I've only shown a few
      - sensor.invet_993
    not_from:
      - unknown
      - unavailable
    not_to:
      - unknown
      - unavailable

Use a template condition to check if the triggering inverter is 30% below the average:

condition:
  - condition: template
    value_template: >
      {{ states(trigger.entity_id)|float(0) < states('sensor.pv_inverter_average_power')|float(0) * 0.7 }}

Send a notification telling you which one is low in the actions:

action:
  - service: notify.foobar # change to your notification service
    data:
      message: >
        The {{ trigger.to_state.name }} power is low.
        
        Average: {{ states('sensor.pv_inverter_average_power')|float(0)|round(0)  }} W

        {{ trigger.to_state.name }}: states(trigger.entity_id) W

If you leave the extra blank lines in there it should create a message like this:

The invert 362 power is low.
Average: 19 W
invert 362: 13 W

you are amazing!
i copied and pasted 95% of your code and now we wait for it to work tomorrow.
actually, let me change the .7 to .95 later, so if anything differs by 5%, then we know the code is working flawlessly.

alias: alert solar panel is not working well
description: ""
trigger:
  - platform: state
    entity_id:
      - sensor.invert_038
      - sensor.invert_164
      - sensor.invert_362
      - sensor.invert_374
      - sensor.invert_456
      - sensor.invert_484
      - sensor.invert_506
      - sensor.invert_669
      - sensor.invert_699
      - sensor.invert_854
      - sensor.invert_861
      - sensor.invert_944
      - sensor.invert_993
    not_from:
      - unknown
      - unavailable
    not_to:
      - unknown
      - unavailable
condition:
  - condition: template
    value_template: >
      {{ states(trigger.entity_id)|float(0) <
      states('sensor.pv_inverter_average_power')|float(0) * 0.7 }}
action:
  - service: notify.telegram
    data:
      message: >
        The {{ trigger.to_state.name }} power is low.

        Average: {{
        states('sensor.pv_inverter_average_power')|float(0)|round(0)  }} W

        {{ trigger.to_state.name }}: states(trigger.entity_id) W
mode: single

What was the 5% you left out?

You can also test it by going to developer tools → states and changing the value of one of the sensors there. It is only a temporary change until it receives its next update.

you are right, i just go to Dev tab and manual set the watt value and the automation was triggered

BUT i get nothing on my Telegram.
is there something wrong with my copy n pasted code from you? the syntax part is always confusing for me to troubleshoot

action:
  - service: notify.telegram
    data:
      message: >
        The {{ trigger.to_state.name }} power is low.

        Average: {{
        states('sensor.pv_inverter_average_power')|float(0)|round(0)  }} W

        {{ trigger.to_state.name }}: states(trigger.entity_id) W
mode: single

That looks ok. If using telegram you can use a message title, emojis and formatting too:

action:
  - service: notify.telegram
    data:
      title: "⚠️<b>The {{ trigger.to_state.name }} power is low.</b>"
      message: >
        Average: {{
        states('sensor.pv_inverter_average_power')|float(0)|round(0) }} W

        {{ trigger.to_state.name }}: states(trigger.entity_id) W
mode: single

Check the automation trace. Maybe the condition stopped the action because the power was not set low enough?

Otherwise check Settings → System → Logs for errors or warnings about the automation or notify service.