In the summer, the add-on heat pump works just like an air conditioner to provide high-efficiency cooling. In winter, it works in conjunction with the existing gas furnace to provide high-efficiency, low-cost heating. During the majority of the heating season, the heat  pump is all you'll need to keep your home comfortable. During the coldest days—typically when the temperature drops below about 25-30 degrees Fahrenheit—the gas furnace will serve as your supplemental heat source. (In an all-electric heat pump system, supplemental heat would be provided by electric resistance coils, like those used in an electric furnace.)

Will an add-on heat pump continue to be more economical than a gas furnace-air conditioner combination? That depends, of course, on what happens with energy costs in the future. However, for the foreseeable future, we expect add-on heat pumps to continue to be more economical for CWLP electric customers to operate than gas furnace-air conditioner combinations.