To determine which model is most appropriate, builders and consumers should compare both the initial cost to buy and install the system and its average annual operating costs. A natural gas heating system may cost more to purchase than an electric system, but it often costs less to operate. In 2001, for example, it cost less to operate even a low-efficiency natural gas furnace than to operate an electric heat pump, and nearly three times as much to heat a home with an electric-resistance furnace as it did to use a high-efficiency natural gas furnace.