How long do central air conditioning systems last?

There are many components of a central air conditioning system: In addition to the condensing unit and air handler or furnace, your home's ductwork, insulation, piping, wiring, thermostat, windows and registers all have important roles in the proper functioning of your central air conditioning system. Generally, it's the condensing unit that fails over time. Usually, the problem is simply a worn out fan motor, burned out capacitor, stuck relay or refrigerant leak. Most central air conditioning systems can be expected to last between 15 and 20 years.