How long does a gas furnace last?

Typically about 15 to 20 years, according to NAHB, Carrier and Lennox. InterNACHI’s chart lists 15 to 25 years.

Is a 20-year-old furnace too old?

It’s at the top of the typical range, but age alone doesn’t tell you its condition. The EPA recommends having HVAC equipment that’s more than 10 years old, or not keeping your house comfortable, evaluated by a professional HVAC contractor.

How can I tell how old my furnace is?

Find the serial number on the rating plate inside the furnace cabinet and decode it. Many newer plates also print the date of manufacture.

How long does a furnace last?

Most sources put a gas furnace’s typical service life at 15 to 20 years. Here’s where that number comes from, what it can and can’t tell you, and how to find your own furnace’s age from its serial number.

The typical range: 15 to 20 years

The National Association of Home Builders’ study of home component life expectancy says “furnaces on average last 15-20 years”. Carrier says “most residential furnaces last 15 to 20 years on average”, and Lennox says “gas furnaces can last 15-20 years”.

Some sources run a little longer. InterNACHI’s life-expectancy chart lists furnaces at 15 to 25 years. In its 2023 furnace efficiency rule, the U.S. Department of Energy estimated an average lifetime of 21.5 years for the most common gas furnaces, and said published estimates range from 16 to 23.6 years. That figure is an average across every furnace, including unusually long-lived ones, so it runs higher than a “typical” range.

Age is a signal, not a verdict

A furnace past 15 years isn’t necessarily failing. How well it was installed and maintained, and how hard it works, matter as much as the date on the plate.

Age is a reasonable prompt for a check-up, though. The EPA says: “If your HVAC equipment is more than 10 years old or not keeping your house comfortable, EPA recommends that you have it evaluated by a professional HVAC contractor.” ENERGY STAR gives the same advice.

How to find your furnace’s age

Turn the furnace off at its switch, then remove the upper access door (the burner or blower compartment). The rating plate is on the inside wall of the cabinet or on the back of the door.

The plate lists the model number and serial number; many newer plates also print a date of manufacture.

The serial number usually encodes when the furnace was made. Enter it below and we’ll decode it using the manufacturer’s documented format. If a serial doesn’t match a documented format, we say so instead of guessing. The date is when the unit was made; it may have been installed later.

Find your furnace’s age

Free, no account needed Photo scanning coming soon

Questions

How long does a gas furnace last?: Typically about 15 to 20 years, according to NAHB, Carrier and Lennox. InterNACHI’s chart lists 15 to 25 years.
Is a 20-year-old furnace too old?: It’s at the top of the typical range, but age alone doesn’t tell you its condition. The EPA recommends having HVAC equipment that’s more than 10 years old, or not keeping your house comfortable, evaluated by a professional HVAC contractor.
How can I tell how old my furnace is?: Find the serial number on the rating plate inside the furnace cabinet and decode it. Many newer plates also print the date of manufacture.

Sources

Last updated 2026-09-29.