A dual fuel system is designed as a halfway point between using the power of a furnace and the energy efficiency of an electrical heat pump. Natural gas furnaces are one of the best ways to provide warmth to a house because of their high heat levels and the availability of natural gas. Heat pumps can help save money using electrical heat, plus they also work as air conditioners.
But because of the cost of using natural gas and the trouble that heat pumps can encounter with extremely low temperatures, the dual fuel system became popular—a heat pump that uses a backup natural gas furnace to help when temperatures drop below 40°F. It does sound like the best of both worlds.
When your furnace or boiler comes on for the winter, or you switch your heat pump into heating mode, you can expect a rise utility bills. That’s the nature of the beast—but the beast doesn’t need to be as fierce or bite as hard as it does. You’re probably paying more for your winter 
