Heater & Furnace Replacement in Houston
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Castle Air Conditioning & Heating replaces gas furnaces, heat pumps and electric heating across southwest Houston, Fort Bend County and the Bay Area. The single thing most Houston homeowners are not told: federal efficiency rules mean heating and cooling are certified as a matched pair, so if your air conditioner is also near the end of its life, replacing both together is usually cheaper than doing it twice. We quote after seeing the house. Call or text (713) 667-7606.
Before you replace anything
Plenty of heating faults are repairs, not replacements. A flame sensor, an ignitor or a capacitor is a repair at almost any age. Start with heater and furnace repair and let us diagnose it properly first. If a carbon monoxide alarm is sounding, leave the house and call 911 or your gas utility before you call anyone else.
The matched-system rule, and why it decides most of this
This is the part that surprises people, so it belongs at the top rather than buried.
Heating and cooling equipment is rated and certified as a matched pair: the furnace or air handler, the indoor coil and the outdoor unit are tested together and the efficiency rating belongs to the combination, not to any one box. Put a new furnace under a fifteen-year-old coil and you do not get the efficiency on the label, you can affect the manufacturer’s warranty, and you have spent money on half a system.
What that means in practice:
- If your air conditioner is young and healthy, replacing the furnace on its own is usually fine.
- If your air conditioner is also near the end of its life, replacing both at once is almost always cheaper than replacing them a year apart, because you pay for one installation instead of two.
- If someone quotes you a furnace without asking the age of your air conditioner, that is worth noticing.
We will tell you honestly which of those three situations you are in. If it is the first one, we will say so and quote the furnace alone.
When replacement is the right call
A cracked heat exchanger. Not repairable. It is what lets combustion gases into the air you breathe, and we will not work around one. This is the clearest replacement case there is.
Age past about fifteen years, plus a significant failure. A blower motor or a control board on a system that old is real money spent on a machine whose other parts are the same age.
Repeat callouts. One fault is bad luck. Three in two seasons is a pattern, and the invoices usually add up faster than people expect.
An air conditioner on its way out. See the matched-system section above. This is the most common reason we end up replacing a furnace that could technically have limped on.
A house that has never been comfortable. If some rooms have never heated properly, the equipment may not be the problem at all. We would rather look at the ductwork than sell you a bigger furnace.
What we install
| Option | How it works | Who it suits |
|---|---|---|
| Gas furnace | Burns natural gas or propane, paired with your air conditioning coil. Usually in the attic or a hall closet in Houston homes. | Houses with a gas supply. Still the most common setup here, and the strongest heat on the coldest nights. |
| Heat pump | An air conditioner that also runs in reverse, so one system heats and cools. No combustion, no flue. | All-electric houses, and anyone replacing heating and cooling together. See heat pumps. |
| Dual fuel | Heat pump plus gas furnace, with a smart thermostat choosing whichever is cheaper at the current outdoor temperature. | Houses with gas that want the efficiency of a heat pump most of the year and the furnace for hard freezes. |
| Electric air handler with heat strips | Electric resistance heat inside the air handler. Simple, no gas, no flue. | Houses with no gas supply, which is a lot of newer Fort Bend County homes. |
| Ductless | A mini split heats and cools one room or a few without ductwork. | Garages, additions and rooms the ducted system never reached. Not a whole-house replacement on its own. |
We are an American Standard Customer Care Dealer and we also install Mitsubishi. We service every make regardless of who fitted it, so we have no reason to steer you toward a badge rather than the right fit for your house.
What actually changes the job
We do not quote heating from a price list, and it is worth knowing why. Two houses on the same street can need meaningfully different work.
| What we look at | Why it matters |
|---|---|
| Correct sizing for the house | Oversizing is the standard mistake. A furnace that is too big short-cycles, heats unevenly and wears itself out. We size to the house, not to what came out of it. |
| The condition of the ductwork | New equipment on leaking or undersized duct will not deliver what it promises. In some houses the duct was the real complaint all along. |
| Attic access and the platform | Most Houston systems are in the attic. Access, the platform condition and the working space all affect the job. |
| Flue and venting | A higher-efficiency furnace vents differently from an older one. That can mean new venting rather than reusing what is there. |
| Gas supply and electrical | Gas line sizing, and the breaker and disconnect for the air handler or heat pump. |
| Condensate | High-efficiency furnaces produce condensate and need a drain, which older installations often do not have. |
| Permits and inspection | Handled as part of the job, and it affects the schedule. |
The safety work that comes with it
Any appliance burning gas produces carbon monoxide, and the flue is what takes it outside. A replacement is the right moment to put that whole side of the system in order rather than inheriting whatever was there.
On a new install we confirm the venting is correct for the equipment, measure the temperature rise, test every safety control, and check you have working carbon monoxide detectors. If we are replacing because of a cracked heat exchanger, we will show you what we found.
The cheapest time to replace is before it fails
Houston’s heating season is short and it arrives all at once. The week of the first hard freeze, every HVAC company in Fort Bend County is booked, equipment availability tightens, and you are making a significant decision in a cold house under pressure.
A planned changeout in a shoulder month gives you time to compare options properly, gives us time to schedule the work, and means you are not choosing in an emergency. If your system is past fifteen years and needed a repair last winter, autumn is the conversation to have. Our Houston maintenance schedule covers keeping the current one going in the meantime.
What the process looks like
| Step | What happens |
|---|---|
| 1. We come and look | At the equipment, the ductwork, the attic access, the venting, the gas and the electrical. And we ask the age of your air conditioner, because of the matched-system rule. |
| 2. You get options in writing | Usually more than one, so you can see what the extra spend buys rather than being handed a single number. |
| 3. You decide | No pressure and no same-day-only pricing. If a repair is still the better spend, we will have said so. |
| 4. We schedule the work | Including anything needed to duct, venting, drainage or electrical while the system is out. |
| 5. We commission it properly | Gas pressure, temperature rise, airflow and safety controls measured and documented, so you know it is right before the first cold night. |
Financing is available subject to approved credit, and it is worth asking about before deciding what to fit rather than afterwards.
Why Houston homeowners use us
- Family owned and working in southwest Houston since 1975
- Licensed under TACLA #00051749C, and insured
- NATE-certified technicians
- American Standard Customer Care Dealer, Mitsubishi installer, and we service all makes
- Gas furnaces, heat pumps, dual fuel, electric heat and ductless
- Written quotes with options, after seeing the house
- 4.9 stars from 200 Google reviews
- We do not buy radio or television advertising, so that cost is not built into your quote
Areas we serve
Castle is based in Fulshear and installs heating across southwest Houston, Fort Bend County and the Bay Area.
Frequently asked questions
Do I have to replace my air conditioner at the same time as the furnace?
Not always, but it is the first question to settle. Heating and cooling are certified as a matched pair, so a new furnace under an old coil will not deliver its rated efficiency and can affect the warranty. If your air conditioner is young and healthy, replacing the furnace alone is fine. If it is also near the end, doing both together usually costs less than doing them a year apart.
How long does a furnace last in Houston?
Often longer than the air conditioner it shares a cabinet with, because our heating season is so short. Fifteen to twenty years is a realistic range to start planning rather than a hard limit. A maintained system comfortably outlasts a neglected one.
Is a cracked heat exchanger repairable?
No. It is what allows combustion gases into the air you breathe, and we will not work around one. If we find a crack we will show you, and it becomes a replacement conversation with the options in writing.
Should I get a gas furnace or a heat pump?
It depends on whether you have gas. If your house is all-electric, a heat pump is usually the clear answer and Houston’s mild winters suit it well. If you have gas, dual fuel gives you both and lets a smart thermostat pick whichever is cheaper at the time. We will tell you which your house actually suits.
Can I just replace the furnace and keep my ductwork?
Usually, but it has to be assessed. New equipment on leaking or undersized duct will not deliver what it is rated for, and a higher-efficiency furnace may also need different venting and a condensate drain that the old installation did not have.
When is the best time to replace heating?
Before it fails, in a shoulder month. The week of the first hard freeze every company in Fort Bend County is booked and you are making a big decision in a cold house. A planned changeout gives you time to compare options properly.
Do you offer financing on a new heating system?
Yes, subject to approved credit. It is worth asking about before deciding what to fit, because it sometimes changes which option makes sense.
Why will you not quote over the phone?
Because sizing, ductwork, attic access, venting, gas supply, electrical and drainage all change the job, and none of them can be assessed down a phone line. A number given without seeing the house is a number that changes later, which helps nobody.
Heater & Furnace Repair in HoustonWhat usually goes wrong, what it means, and when a repair is still the better spend.
Published by Castle Air Conditioning & Heating. Family owned since 1975. Licensed TACLA #00051749C. NATE-certified technicians serving Houston, Fort Bend County and the Bay Area. Quotes in writing before work begins. Last reviewed September 2026.
Thinking about replacing your heating? Call or text (713) 667-7606.