Consumers and inspectors and other professionals advising their clients should note that these life expectancies have been determined through research and testing based on regular recommended maintenance and conditions of normal wear and tear, and not extreme weather (or other) conditions, neglect, over-use or abuse.  Therefore, they should be used as guidelines only, and not relied upon as guarantees or warranties.     

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Thermostats may last 35 years but they are usually replaced before they fail due to technological improvements.  

HVAC  

YEARS  

Air Conditioner (central)  

7 to 15  

Air Exchanger  

15  

Attic Fan  

15 to 25  

Boiler  

40  

Burner   

10+  

Ceiling Fan  

5 to 10  

Condenser  

8 to 20  

Dampers  

20+  

Dehumidifier  

8  

Diffusers, Grilles and Registers  

25  

Ducting  

60 to 100  

Electric Radiant Heater   

40  

Evaporator Cooler  

15 to 25  

Furnace  

15 to 25  

Gas Fireplace  

15 to 25  

Heat Exchanger  

10 to 15  

Heat Pump  

10 to 15  

Heat-Recovery Ventilator   

20  

Hot-Water and Steam-Radiant Boiler  

40  

Humidifier   

12  

Induction and Fan-Coil Units  

10 to 15  

Chimney Cap (concrete)  

100+  

Chimney Cap (metal)  

10 to 20  

Chimney Cap (mortar)  

15  

Chimney Flue Tile  

40 to 120  

Thermostats   

35  

Ventilator   

7  

  

Note : Life expectancy varies with usage, weather, installation, maintenance and quality of materials.  This list should be used only as a general guideline and not as a guarantee or warranty regarding the performance or life expectancy of any appliance, product, system or component.    

Source: http://www.nachi.org/life-expectancy.htm