It depends on the furnace. A good rule of thumb is to replace a furnace when it's 10 years old, but some furnaces can last up to 15 years. Factors that affect how long a furnace lasts include the quality of the installation, how often it's serviced, and the type of fuel it uses. If you're considering replacing your furnace, consult with a qualified HVAC contractor to get an estimate on what a new furnace would cost and how much it would save you in energy costs over time.

A furnace should be replaced when it is no longer able to provide the homeowner with the comfort they desire. A good rule of thumb is when the furnace is more than 15 years old, it's time for a replacement.