How long does a furnace last?
A gas furnace typically lasts 15 to 20 years. That's the range most inspector and industry references agree on; the sources are listed below. Your unit's age is in its serial number.
| Type | Typical life | What the sources say |
|---|---|---|
| Gas furnace | 15 to 20 years | NAHB / Bank of America Home Equity: Study of Life Expectancy of Home Components (Feb. 2007), copy hosted by NSF: Furnaces 15 to 20 years; warm-air gas furnaces 18; Carrier: How Long Does a Furnace Last?: Gas furnace 15 to 20 years; up to 30 for high-quality units; Lennox: How Long Does a Furnace Last?: Gas furnaces 15 to 20 years; InterNACHI's Standard Estimated Life Expectancy Chart for Homes: Furnace: 15 to 25 years; DOE final rule, consumer furnaces, 88 FR 87502 (Dec. 18, 2023): Mean lifetime 21.5 years for non-weatherized and mobile-home gas furnaces; literature range 16 to 23.6; New York Joint Utilities TRM, Appendix P: Effective Useful Life (Dec. 2019), hosted by NYSERDA: Gas-fired furnace: 22 years; ENERGY STAR: When Is It Time to Replace?: Consider replacing a furnace more than 15 years old |
What shortens it
- The wrong size. An oversized furnace cycles on and off too often, an undersized one runs almost nonstop, and both wear parts faster.
- Installation faults: leaky or undersized ducts, poor condensate drainage on high-efficiency models, or badly fitted gas lines.
- Skipped maintenance and dirty filters, which restrict airflow and strain the blower motor.
- Long, cold winters or a high thermostat setting, which add run hours.
- Year-round blower use, because the furnace also moves the air for central air or a heat pump.
Signs it's time to plan a replacement
- It is more than 15 years old.
- Breakdowns are frequent, or one repair would cost about half the price of a new furnace.
- Energy bills keep climbing with no change in use.
- Some rooms stay cold, or it can't hold the thermostat setting.
- It blows cold air or makes new, loud noises.
Common questions
How long does a gas furnace last?
Typically 15 to 20 years. Installation, maintenance and conditions move the real number either way.
How do I find out how old my furnace is?
The manufacture date is coded in the serial number on the data plate. Type it into the decoder to read the month and year.