Look, I postet it here (especially post #6 with pictures) but unfortunately besides a recommendation to ensure all sensors are available in the calculation I got no clue so I just focused on how to proceed with the outcome.
Anyway, my current calculation is as follows:
Rest of house consumption = Total consumption - wallbox - heat pump. All meters are following their source since a specific date I set.
After that I divide by the days since that specific date and multiply by 365 to get my yearly estimate based on my consumption.
That’s about it. Works quite okay, besides the sabertooth thingy, that is there especially when consumption is high (e.g. charging the car).
And my assumption is that it is because the total consumption meter does not go up in the exact millisecond as the wallbox consumption thus leading to sabertooth line in my calculated “rest of house” consumption template sensor.