When you are resetting circuit breakers or changing fuses too often. When you turn on your air conditioner and the lights dim in the room. When your lights flicker or go on and off. When you can smell wire burning. When you have six electronic devises going into one outlet in back of your electronics center. When you have receptacle outlets overburdened by multi-plug strips. When a three-prong plug needs a two-prong adapter. If you have to run extension cords to plug in electrical devices.