Simple electricity meter manual input

Installation
2

You need to tell to your template sensor where it will read it’s value.
This is the state: part of the configuration, wich obviously is NOT in your configuration.

I would recommend to read : Template - Home Assistant

Then here is what’s missing from what I’ve understood of your setup :

template:
   - sensor:                                                                                                                  
      - name: energy_reading                                                                                                    
        unit_of_measurement: kWh                                                                                                
        device_class: energy 
        state: >-
          {{ states('sensor.energy_reading') | int(default=0) }}

But, if you set an initial value to your input_number it will go back to this value after every HA restart. You should not set the initial value, wich will lead to the input_number to get back the last value it has before HA restart.

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