Water heaters in general have an average estimated useful service life of 10-12 years, though water quality, routine upkeep/maintenance, and location of the water heater will all play critical roles in the longevity of these systems.

Gas-fired forced air furnaces in general have an average estimated useful service life of 15-20 years, though routine upkeep/maintenance, and location of the furnace will all play critical roles in the longevity of these systems.

Split system air conditioners and heat pumps in general have an average estimated useful service life of 10-12 years, though routine upkeep/maintenance, regional weather/climate, and location of the condenser unit will all play critical roles in the longevity of these systems.

The average service design life of boilers can vary from as little as 10 years to as many as 50 years depending on the type and quality of materials used in their manufacture. Routine upkeep/maintenance, regional weather/climate, and location/placement of the mechanical systems will all play critical roles in the longevity of these systems.