All you can measure by plugging into a wall socket is (1) voltage; (2) power, but only for devices plugged into that outlet (by installing a meter like a kill-a

All you can measure by plugging into a wall socket is (1) voltage; (2) power, but only for devices plugged into that outlet (by installing a meter like a kill-a-watt between the outlet and the device). In order to determine power consumption for an entire circuit, or your entire house, you need to put a sensor around a wire in the breaker box. You can’t even do it in the walls because once power cabling leaves your breaker box, all the conductors for a given circuit are bundled, and if you put a current transformer around that bundle, it will show net zero power because it’s summing both halves of the AC wave. You need to get a sensor around just the hot wire of the circuit, which is only accessible on its own inside the breaker box.