Today's heating, ventilation and air conditioning units are more energy-efficient than their predecessors.
New air conditioning and heating equipment lasts longer than ever. The end of a furnace's or air conditioner’s service life depends on more than just chronological age. Energy-efficiency issues and the price of any necessary repairs versus the cost of upgrading to a new unit all enter into that determination.
The average service life of a new furnace is 16 to 20 years. Most furnace parts that fail during that span are replaceable at a cost that makes repair a better call than replacing the entire furnace. The exception is the heat exchanger, a furnace's single most expensive component. A cracked heat exchanger in a unit that’s already out of warranty is usually a tipping point that means it’s time to shop for a new furnace.
Central air conditioners typically last from 12 to 15 years. The lifespan of a central cooling unit may be reduced if its capacity is not properly matched to the cooling load of the home. Oversized air conditioners “short-cycle,” turning on and off rapidly, inflicting excessive wear and tear on the compressor. Like the furnace heat exchanger, the compressor is the most costly part in the system. A worn-out compressor in a unit that’s outlived its warranty is usually a deal-breaker that warrants upgrading to a new, more energy-efficient air conditioner rather that repairing the existing unit.