I worked for decades in the utility space. After my utility had deployed their smart meters we had a company come in and show us a product they had where they could tell you if someone had an electric furnace, and if so, they could tell you the make and model! They were fairly accurate on refrigerators as well.

Mind you, we were looking at using that data to be able to determine whether to inform that customer that they could buy more efficient appliances and show them the amount of money they could save. We ended up not pulling the trigger on that initiative but that's not the point: we could have.