Should You Repair or Replace Your Furnace?

This is for a furnace that has actually failed or is showing a specific fault. If yours is just old and you're planning ahead rather than diagnosing something broken, how long a furnace lasts covers the timeline instead. Two things decide this: what actually failed, and how old the furnace already is.

What's actually wrong, and what it costs to fix

These are commonly repairable faults. Whether the repair is worth doing depends on the furnace's age, its repair history, and the quote itself — check the furnace's age first if you're not sure where yours falls:

A cheap part on a 6-year-old furnace and the same part on an 18-year-old furnace with two prior repairs aren't the same decision, even at an identical quote — the sections below cover what changes that.

Is this a minor fix, or a sign the furnace is done?

None of these are automatic rules on their own — they're the factors that shift the answer toward replacement as they stack up:

• The furnace is 15 or more years old. Past that point, a repair beyond a cheap sensor or igniter is worth weighing against a new unit rather than assumed worth doing — not because the furnace is definitely done, but because it's closer to the end of its typical 15–20 year life than the start.
• Repairs have become frequent. One repair is normal wear. A second major failure within a couple of years is a stronger signal the furnace is entering decline, though not on its own a guarantee the next part won't hold.
• The repair quote approaches roughly half the cost of a new furnace. The closer it gets, the less sense it makes to spend that much on equipment that isn't new and doesn't come with a fresh warranty.
• A heat exchanger issue, on an older furnace. Covered in detail below — age is what tips this one specifically toward full replacement rather than a component repair.

We deliberately didn't include "rooms won't heat evenly" as a replacement trigger — uneven heating is just as often ductwork, dampers, insulation, zoning, or thermostat placement as it is the furnace itself, and diagnosing it as a furnace problem without ruling those out first is a guess dressed up as a rule.

A cracked heat exchanger is a safety issue — but confirm the diagnosis

The heat exchanger is the metal chamber the burner fires into; house air passes over the outside of it and picks up heat without touching the combustion gas. When it cracks — from years of expanding and contracting, or from overheating behind a clogged filter — that separation is gone, and exhaust including carbon monoxide can mix into the air going to your rooms.

Make sure your home has working CO alarms before this ever becomes a question you're asking mid-crisis. The CPSC recommends installing battery-operated or battery-backup CO alarms on every level of the home and outside sleeping areas, following the alarm manufacturer's own placement instructions.

If a technician tells you it's cracked:

• Stop using the furnace if they confirm unsafe operation.
• Ask to see the evidence — a visual inspection, a combustion analyzer reading, or camera footage. This is an expensive diagnosis on top of being a safety one, which is exactly the combination worth verifying rather than taking on faith.
• Check whether the heat exchanger is still under warranty. Most manufacturers cover it for 10–20 years separately from the rest of the furnace, and Carrier's own pricing lists heat exchanger replacement as a real repair line item, roughly $500 to $1,500, not automatically a whole-furnace job.
• On an older furnace, full replacement usually makes more economic sense — you'd be paying a real repair bill on a unit that's likely near the end of its life anyway.
• On a younger furnace with warranty coverage, replacing just the heat exchanger can still be the right call — get a second opinion before committing to either path, since this is one of the more expensive misdiagnoses to get wrong in either direction.

The math: age, repair cost, and the $5,000 rule

A screening tool, not a decision engine, for anything that doesn't already fall into the categories above: multiply the furnace's age by the repair quote. Past roughly $5,000, it's worth taking the replacement conversation seriously.

• 10-year-old furnace, $400 repair → $4,000 → generally still worth repairing
• 14-year-old furnace, $400 repair → $5,600 → lean toward replacement
• 8-year-old furnace, $650 blower motor → $5,200 → borderline; repair if the rest of the furnace is clean

It's a rough heuristic, not a law — it helps identify when a sizeable repair is being spent on equipment with limited remaining life, nothing more precise than that.

Replacement looking like the better option? See what a new furnace typically costs and what to expect before requesting quotes — most homeowners land between $2,800 and $6,900 installed.