I have two different sensors measuring power at two different points of the house: a Shelly EM at the meter measuring total power consumption and a Shelly Plus 1PM measuring power used by the water heater.
I’m interested in knowing the instantaneous power consumption of the house, excluding the heater.
I was thinking of making a template sensor computing the difference between the two but since the two sensors will update asynchronously from one another, I suppose I’m going to get bogus values whenever the heater switches from ON to OFF or the other way around.
Any best practices for this kind of problem?