I’ve had a false positive with my power usage based approach:
The usage on the left is from my electric oven. On the right it’s the ironing board. By chance the iron board pattern triggered my automation for my dishwasher 
But i’m still happy with it.
Just to add my personal use case as well:
I have an EV and I would like to track it’s monthly consumption (30 days).
I have a wallbox which I use to know how much I charged as well as an input number to manually set the charged amount outside of my home.
However for the real consumption I would have to add the difference of the battery level from 30 days ago and now. So if 30 days ago I had 80% battery and now I have 50% I consumed 30% of 60kWh, so I have to add another 18kWh to the total consumption.
