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Whether To Replace Or Fix Old Furnace

When older equipment starts to fail, it’s important to decide whether to replace or fix old furnace equipment.


A gas furnace has many functions and multiple components. Its primary purpose is to pull in the surrounding air, clean it with an air filter, heat the air with a stainless steel heat exchanger (warmed by a gas burner), and blow the warmed air through the attached ductwork. A blower motor is used to propel the warm air through the ducts.

The efficiency of a heating system is gauged by its AFUE (Annual Fuel Utilization Efficiency). This rating is based upon how much fuel and energy are being transformed into heat. For example, an AFUE rating of 60 means only 60 percent of the unit’s fuel is being used for heat. The remaining 40 percent becomes lost through exhaust.

Modern gas-fired models employ a closed-combustion, two-stage system. It can achieve AFUE ratings of nearly 98 percent. According to the United States Department of Energy, models that were produced in the 1960s have AFUE ratings of 60. Ratings of those manufactured in the 1970s and early 1980s are 65, and models produced during the middle of the 1980s are 68. Improvements made during the late 1980s and early 1990s raised them to 76, which was followed by an increase to 78 after 1992.

Typical heating systems have lifespans of 25 years. However, even if they’re still functioning, they may be wasting energy. Professionals suggest repairing heating systems that are less than a decade old. Otherwise, the savings from the increased energy-efficiency and environmental-friendliness of modern models will outweigh the costs of upgrading the system.

When deciding whether to fix old furnace components, it’s important to consider its age. While replacing the unit with an updated model will cost more up front, the long-term savings will be considerable. Modern power-vented, closed-combustion units are designed with enhanced efficiency and safety. They are not susceptible to exhaust backdrafting, or dispersions of carbon monoxide due to corroded or cracked heat exchanges.