How to determine if my airconditioning has been turned on

Hey Everyone,

I’m looking for some ideas around how i could determine if my home airconditioning system has been powered on. If i can identify that the aircon was powered on then i could for example do some checks to see if any external windows or doors are open & take some action accordingly.

I have these functioning devices in home-assistant that i can work with but i need some community thoughts around the best way to achieve this.

Existing components i can use:

  • Whole house power monitoring via a Shelly3EM shows me net usage (grid consumption minus solar return). But no separate monitoring of the aircon circuit.
  • A dumb reverse-cycle ducted aircon system
  • Various integrated temperature & humidity sensors around the inside of the house
  • Some external temperature measurement, including an integrated smart weather station

I’m struggling to come up with a reliable way to “assume” the aircon was turned on. Perhaps i could look for a relatively rapid temperature or humidity drop inside the house but i’m unsure what’s the best way to even know that (statistics sensor?). I could also potentially monitor for a rapid power consumption spike but other appliances could also give a false positive (like iron, kettle, oven). Maybe a combination of power use & temp changes, but how best to do that?

Clearly my best option is to have a separate power monitoring device on the specific power circuit that feeds the aircon system but right now that’s not an option. So i’m hoping someone might have some thoughts on this.

Cheers
Nick