Furnace Repair vs. Replacement in Houston

The quick answer

Houston furnaces do not run much — maybe two or three months a year — so they often last longer in calendar years than they would up north. But that also means small problems hide until the first real cold snap.

The rule of thumb: if the furnace is under about 15 years old and the repair is minor, fix it. If it is past 15 years, has a cracked heat exchanger, or the repair is a big fraction of a new unit, replace it.

Heating rarely fails in October. It fails on the first freezing night — which is exactly when a repair costs the most and techs are slammed.

What furnace repair costs in Houston

A flame sensor or igniter is a cheap, common fix. A cracked heat exchanger is the one that usually ends the conversation — more on that below.

When to replace instead of repair

Age (15 to 20 years)

Past 15 years, parts get harder to find and efficiency lags. If your AC is also aging, replacing both together is often cheaper than two separate jobs.

A cracked heat exchanger

This is the big one. A cracked heat exchanger can leak carbon monoxide into your home, and the repair often costs nearly as much as a new furnace. In most cases this is a replace, not a repair.

Repeat repairs

If you have paid for two or three heating repairs in a few winters, you are funding the next failure. Add it up before approving another.

WARNING: Carbon monoxide from a cracked heat exchanger or a bad furnace is odorless and deadly. If your CO detector sounds, or you feel headachy/dizzy when the heat runs, leave and call for help — do not troubleshoot. Every Houston home with gas heat should have working CO detectors.

The Houston angle

Because our heating season is short and sharp, furnaces here sit idle for months and then get hammered during a hard freeze — like the 2021 winter storm that caught thousands of Houston homes with heating they had not tested in a year.

Two practical takeaways:

• Test your heat before winter, not during the first freeze. A September test gives you time to fix it calmly and cheaply.
• Many Houston homes use heat pumps rather than gas furnaces; the repair-or-replace math is similar, but a failing heat pump also affects your summer cooling, which raises the stakes.

A furnace that has not run since last February is a furnace you have not actually tested. Fire it up early.

When repair is the right call

• The furnace is under 15 years old.
• The failure is an igniter, flame sensor, thermostat, or blower — not the heat exchanger.
• Your CO detectors are clear and it has been reliable.

Fix it, and put a pre-winter test on your calendar.

TIP: When you call, have the furnace's age, the model number, and what it is doing (no ignition? blowing cold? short cycling?) ready. And ask the tech to confirm the heat exchanger is intact — it is the safety-critical part.

Frequently Asked Questions

How much does furnace repair cost in Houston?

Most Houston furnace repairs run $150 to $900 — igniters, flame sensors, thermostats, and blower motors are on the lower end, while gas valves and control boards run higher. A heat-exchanger problem is the exception and usually points toward replacement.

Is it worth repairing a 15-year-old furnace?

Sometimes. A minor repair on a 15-year-old furnace that has been reliable can be worth it, but a major repair — especially the heat exchanger — usually favors replacement, particularly if your AC is also aging and could be replaced at the same time.

How much does it cost to replace a furnace in Houston?

A professionally installed gas furnace typically runs $3,500 to $7,500 depending on size and efficiency. If you are replacing an aging AC at the same time, bundling the two is often cheaper than doing them separately.

Should I repair or replace a cracked heat exchanger?

Usually replace. A cracked heat exchanger can leak carbon monoxide, and the repair cost is often close to the price of a new furnace, so replacement is typically the safer and smarter choice.

When should I call a licensed HVAC pro?

Call a pro for anything involving the gas valve, the heat exchanger, or a carbon-monoxide concern. You can safely check that the thermostat is set to heat and that the breaker has not tripped, but gas heating repairs need a licensed professional.