 All electric resistance heaters are 100% efficient, with operating costs determined by their wattage and the length of operating time.A 500 watt heater will take at least twice as long to reach the same thermostat setting as a 1000 watt unit; the total consumption of electricity is the same for both.By contrast, an electrical heat pump used for home heating typically has an efficiency well above 100%, expressed as its coefficient of performance.