[mjdiloreto]

Energy use for constant audio monitoring would make that implementation impractical compared to simply monitoring the energy draw from the device.

[tnmom]

A Pi draws somewhere under 10W at peak, probably significantly under that most of the time. That’s about 87kWh per year, worst case.

Something like $8-16 dollars depending on how incompetent your power company is - well under the threshold for anyone who knows how to do this kind of work to worry about. Again, worst case; I’d bet you can do constant listening half that.

[Void_Kitty]

You could probably run this on a 32bit micro controller doing less than a watt