1) We can tell by the brightness of our lights and the speed of our fans if the power is operating at the full 220v, closer to 240v or closer to 110v.
2) Every time we walk in the house we listen for the hum of the fridge, if we don't hear it we flick the kitchen light switch on and praise Jesus eleven times when it's actually ON.
3) We can de-bone a chicken faster that you can say "throw away the neck first!"