How Long Does a Furnace Last? (And When to Replace Yours)

Short answer: a well-maintained gas furnace typically lasts 15–20 years. Skip maintenance and that can drop to 10–12; take care of it and some units push past 20. If yours is over 15 and repairs are getting more frequent, it's time to compare the cost of the next repair against a replacement.

What shortens a furnace's life

• Dirty filters. A clogged filter makes the blower work harder and overheats the heat exchanger — the most expensive part of the furnace.
• Skipped maintenance. Small issues (a weak igniter, a dirty flame sensor, a failing capacitor) become big ones when they're never caught.
• Wrong sizing. An oversized furnace short-cycles — constant starting and stopping wears components out years early.
• Poor installation. Bad ductwork, venting, or gas pressure from day one takes years off the equipment. It's why who installs it matters as much as what's installed.

Signs your furnace is near the end

• Repairs every season instead of every few years
• Rising gas bills with no change in usage — efficiency degrades with age
• Uneven heat, long run times, or short cycling
• Yellow burner flame instead of blue, or rust and cracks around the unit
• It's 15+ years old and the current repair quote is a big one

Repair or replace: the honest math

A common rule of thumb: if the repair costs more than a third of replacement and the furnace is past 12–15 years, replacement usually wins. A new gas furnace installed by Lumen runs $2,000–$4,000 — real numbers on our pricing page — and PGW's EnergySense program currently pays a $400 rebate on 95%+ AFUE furnaces in Philadelphia. See our full furnace cost guide for what drives the price.

Buy years with basic care

Change the filter regularly, keep vents open and unblocked, and get a professional tune-up each fall — our fall maintenance checklist covers the routine. If your furnace is acting up right now, start with our troubleshooting guide, then call (267) 252-2969 — our heating repair service call is $150 and includes a full diagnosis.