1. Get an estimate in writing for repairs, and compare it to the cost for a new system. If the repairs will cost more than one-third of a new unit, buying a new energy efficient system may make the most sense.
Tom Eppers, co-owner, Dowe & Wagner, a heating, ventilation, and air-conditioning company serving residential and commercial customers in Illinois and Wisconsin, states, “Heating and air-conditioning systems are the biggest users of energy in the home, responsible for up to 75 percent of the utility bill. A new high-efficiency furnace can save up to 50 percent in operating costs over a 10-year-old furnace.”
However he adds that often simple repairs can allow an older system to provide a few more years of reliable service. Furnaces on average last 15 to 20 years. But when safety issues arise, such as a cracked heat exchanger which may leak toxic carbon monoxide gas, replacement is recommended.