Split sensor when you only know the value of both together and one of them?

Hi guys,
Need some help…

Today I have a sensor that reads the combined power out of the two entities (unfortunately)…

  • nibe_power
  • element_power

I also have a separate sensor on the element_power so I always know what the power is for that particular sensor.
I would like to get what the power consumption is on the nibe_power at any given time so my thought was off course to go with nibe_power - element_power… but…

The thing is that they are not always pushing power so my first attempt showed -1000 W since nibe_power did not deliver any power at the time when element_power used 1000 W.
Same goes if nibe_power is running on 400W and element_power is at 600W…same outcome basically.

Is this acchievable?

This was my starting point which I noticed is not what I was after…

value_template: "{{ (states('sensor.nibe_power') | float) - (states('sensor.element_power') | float) | round }}"