The short answer

AC unit replacement cost depends on the system your house actually needs: its size from a load calculation, the SEER2 efficiency rating, single-stage or variable-speed operation, a matched indoor coil, the refrigerant, the condition of your ducts, attic access and the permit. A written quote that itemizes each of these is the only reliable number.

What changes an AC replacement, at a glance

Why can't anyone quote an AC unit replacement cost over the phone?

Because "a new AC unit" is not one thing. Replacing a central air conditioner can mean anything from setting a new outdoor unit on an existing pad to replacing the outdoor unit, the indoor coil and the air handler, reworking the ductwork, running a new line set through the attic and upgrading the controls. Each of those is a different job.

The honest answer depends on things nobody can see from a phone call: how much cooling your house actually needs, what the attic looks like, what shape the ducts are in, which refrigerant your current system uses and whether the line set can stay. That is why this guide does not deal in numbers. It explains what goes into the job, so that when a contractor hands you a quote, you can read it, question it and compare it with another one.

How is the right size for a new AC worked out?

Residential air conditioners are sized in tons of cooling capacity, and the size is the first thing that shapes the job. A larger system is more equipment. But the more important point is that the right size is not simply "bigger is safer."

Why a load calculation beats square footage

The right size comes from a load calculation: a room-by-room look at how much heat your house gains, based on its insulation, windows, the direction it faces, the attic, the ductwork and how many people live there. Square footage alone, or matching whatever size the old unit was, is a guess. The old unit may have been the wrong size for twenty years, and the house may have changed since, with new windows, added insulation or an enclosed patio.

What goes wrong with an oversized system in Houston?

Oversizing is the more common mistake here, and Houston punishes it. An air conditioner removes moisture from the air while it runs. An oversized unit cools the house quickly, hits the thermostat setting and shuts off before it has run long enough to pull much water out of the air. The result is a house that reads the right temperature but seems cold and damp at the same time. Short cycling also means more starts, and every start is wear on the compressor.

And an undersized one?

An undersized system runs constantly on the hottest afternoons and still falls behind. Getting the size right is what lets efficiency, staging and humidity control do their jobs.

What does the SEER2 rating change?

SEER2 is the Seasonal Energy Efficiency Ratio, measured under the testing method the U.S. Department of Energy adopted in 2023. It describes how much cooling a system delivers for the electricity it uses over a cooling season. A higher number means the system uses less electricity to do the same work.

What is the minimum SEER2 in Texas?

Federal efficiency standards set a floor, and it depends on where you live. Texas is in the Department of Energy's Southeast region. According to the Air-Conditioning, Heating, and Refrigeration Institute (AHRI), split-system air conditioners in the Southeast must reach at least 14.3 SEER2 below 45,000 Btu/h and 13.8 SEER2 at 45,000 Btu/h and above. The rule is enforced by installation date: units that do not meet it cannot be installed on or after January 1, 2023. Any system a contractor installs in Houston today has to meet that floor, so every legitimate quote should list the SEER2 rating.

How much efficiency makes sense in Houston?

Higher-efficiency equipment is built differently, with larger coils and, at the top of the range, variable-speed compressors and blowers. The case for more efficiency is stronger here than in a mild climate, because a Houston system runs for more of the year and more hours a day. How far up the range makes sense depends on how long you plan to stay in the house and how much the comfort benefits below matter to you.

Single-stage, two-stage or variable-speed: what is the difference?

This choice changes the compressor, the indoor blower and often the thermostat, and it has as much to do with comfort as with efficiency.

Single-stage

A single-stage system is either fully on or off. It is simple and proven, and on a correctly sized system it does the job. On mild, muggy days it tends to run short cycles, which is when humidity control suffers most.

Two-stage

A two-stage system has a lower setting it uses most of the time and a higher one for the hottest afternoons. Running on the lower stage means longer, gentler cycles, which pull more moisture out of the air and even out temperatures between rooms.

Variable-speed

A variable-speed, or inverter, system adjusts its output across a wide range to match what the house needs moment to moment. It runs long and slow most of the day, which is the best way an air conditioner can dehumidify. These systems tend to be the most efficient and the quietest, and they often need a matched or communicating thermostat to control them properly.

Why does the indoor coil and air handler matter?

A central air conditioner is two halves: the condenser outside and the evaporator coil inside, usually sitting on or in the air handler or furnace. In many Houston homes the indoor half is in the attic.

What is a matched system?

For split systems, AHRI certifies the performance of the system rather than the individual units. Each certified combination of indoor and outdoor unit gets its own certified reference number, and the SEER2 rating belongs to that combination, not to the outdoor unit alone. You can look up a combination in the AHRI Directory, and the certificate it produces is proof that the system you bought is a certified match.

Can you replace just the outdoor unit?

Sometimes, and it is a smaller job. But a new outdoor unit paired with an old coil may never reach its rated efficiency, and an old coil may not be suited to the refrigerant a new outdoor unit uses. If the indoor coil is near the end of its life too, you may be doing the job twice. It is a fair question to ask, and it is worth asking why a contractor recommends one approach or the other.

How does the refrigerant change affect a new AC?

Refrigerant is the part of this decision that has changed most in the last few years, and it is worth understanding before you compare quotes.

What changed on January 1, 2025?

Under the U.S. Environmental Protection Agency's Technology Transitions rule, new residential and light commercial air conditioning and heat pump systems manufactured or imported from January 1, 2025 must use a refrigerant with a global warming potential below the rule's limit of 700. That moved new equipment away from R-410A, the refrigerant most systems of the last two decades use, and toward alternatives such as R-454B, which the EPA lists as acceptable, subject to use conditions, for new residential equipment.

Can contractors still install R-410A systems?

The EPA's current summary of the rule sets no installation deadline for systems where all the specified components were manufactured or imported before January 1, 2025, and the EPA has revised the installation rules more than once during the transition. So you may see quotes for newer-refrigerant equipment and for remaining R-410A stock side by side. Neither is wrong, but they are different long-term decisions, so ask which refrigerant each quote uses and what that means for servicing the system over its life.

What if my current system runs on R-22?

Many older Houston systems still use R-22, often sold under the Freon name. According to the EPA, no new R-22 has been made or imported in the United States since January 1, 2020. You may keep running an R-22 system, but it can only be serviced with recycled, reclaimed or previously produced refrigerant, and the EPA says there are no drop-in replacements. If you have an R-22 system, a replacement means a whole new refrigerant circuit, which usually means the indoor coil too.

Does your ductwork need work too?

A new air conditioner is only as good as the ducts that carry its air. Many Houston homes have ductwork running through a hot attic, and if those ducts leak, the system is paying to cool the attic.

• Leaks and disconnected runs waste cooled air and pull hot, humid attic air into the system.
• Crushed, kinked or sagging flex duct starves rooms of air, which is often the real reason one bedroom never cools.
• Undersized ducts or too little return air restrict airflow, which costs efficiency and can shorten the life of the new equipment.

Duct repair or replacement is one of the biggest things that can separate one quote from another. If a quote includes duct work, it should say which runs, and why.

How does Houston humidity shape the system you need?

In most of the country, an air conditioner is judged on temperature. In Houston, humidity is half the job. Air conditioners remove moisture as they cool, but only while they run, and only if air moves across the coil slowly enough to condense water out of it.

That is why sizing, staging and blower speed matter so much here. A right-sized, two-stage or variable-speed system with good airflow does a far better job of drying the house than an oversized single-stage one. Some homes need more than the air conditioner can do on its own, particularly on mild, damp days when the house barely needs cooling but the air is heavy. That is where a whole-home dehumidifier, installed with the ductwork, comes in. Ross Air installs whole-home dehumidification, and it is worth raising during a replacement estimate if your house seems clammy, smells musty or shows condensation on windows.

Why does where the equipment sits change the job?

Installation complexity is one of the least visible parts of a replacement and one of the most important.

Attic access

Getting an air handler and coil in and out of an attic through a narrow hatch, across joists and around framing takes time and care. In summer the heat in the attic slows everything down.

The platform, drain pan and float switch

Attic equipment sits over your ceiling, so the drain system matters. A rusted secondary drain pan, a missing float switch or a poorly pitched condensate line is best fixed while the old equipment is out. A good quote says whether these are being replaced.

The line set, pad and electrical

A long or hard-to-reach line set run, a sunken or cracked outdoor pad, or an electrical disconnect and wiring that do not suit the new unit all add to the job. None of these is unusual; they just need to be on the quote rather than discovered on the day.

Do you need a permit to replace an AC in Houston?

Inside the City of Houston, yes. The Houston Permitting Center requires a permit for the installation, repair or replacement of condensing units, and a mechanical permit to alter an existing HVAC system. Typically the mechanical contractor doing the work calls in the required inspections. Cities around Houston and unincorporated areas have their own rules, so if you live outside the city limits, ask the contractor which authority applies.

Does the thermostat need replacing too?

Sometimes. A basic single-stage system often works with the thermostat you have. Two-stage systems need one that can call for both stages, and many variable-speed systems only reach their full capability with the manufacturer's matched or communicating control. If you like your smart thermostat, ask whether it is compatible.

How do brand and warranty affect the choice?

Ross Air installs Trane and Goodman equipment. Within each brand there are several product lines, from single-stage to variable-speed, so the product line and the installation usually matter more to how a system performs than the name on the cabinet.

Manufacturer warranty and registration

Manufacturer parts warranties differ by brand and product line, and many depend on the equipment being registered with the manufacturer within a set window after installation. Miss it and the coverage may be shorter. Ross Air helps customers whose systems it installed register their equipment, so ask who is handling registration and get confirmation once it is done.

Workmanship warranty

The manufacturer covers parts. The installer covers the installation, and that is a separate promise with its own terms. Ask what the installer's workmanship warranty covers and for how long, and get it in writing.

Is financing available?

Ross Air's replacement and installation page says financing is available. If you are considering it, ask about the terms during your estimate so you can compare them alongside the equipment and the installation.

Should you repair or replace your AC?

Most replacements start with a repair question. The system has failed, or a technician has found a big problem, and you have to decide whether to fix it or move on. There is no formula that answers it for every home, but a few honest tests help.

What failed?

A capacitor, contactor or clogged drain line is a small repair on almost any system. A failed compressor, a leaking evaporator coil or a condenser coil is a major repair, and on an older system it is usually the point where replacement deserves a serious look.

How old is the system, and how has it been maintained?

A system near the end of its working life that needs a major component is a poor place to put a big repair, because the next part is likely not far behind. A younger system with the same failure, especially one still under warranty, is usually worth repairing.

Which refrigerant does it use?

An R-22 system that needs refrigerant work is one of the clearest signals to replace. An R-410A system is still serviceable, but the long-term refrigerant picture is part of the decision, especially for a repair that opens the refrigerant circuit.

Are the repairs becoming a pattern?

One repair is a repair. Three in two summers is a system telling you something.

Does the house stay comfortable?

Rooms that never cool, a house that stays damp, and a system that runs all afternoon without catching up are problems a repair will not solve.

If you are weighing a major repair, ask for both options at once: the repair, and what a replacement would involve. A reputable contractor will lay out both and let you decide.

What should a good written replacement quote include?

A good quote reads like a description of the job. You should be able to hand it to someone else and have them understand exactly what is being installed and what is being done. At a minimum, look for:

• The system size in tons or Btu/h, and how it was determined.
• Model numbers for the outdoor unit, the indoor coil and the air handler or furnace.
• The AHRI certified reference number for that combination, and its SEER2 rating.
• The refrigerant the new system uses.
• Staging: single-stage, two-stage or variable-speed.
• The line set: new or reused, and why.
• Ductwork: what was inspected, and what, if anything, is being repaired or replaced.
• Attic items: platform, secondary drain pan, float switch, condensate line.
• Outdoor items: pad, electrical disconnect and wiring.
• The thermostat, if one is included.
• The permit, and who schedules the inspections.
• Removal of the old equipment and recovery of its refrigerant.
• Warranties: manufacturer parts terms, registration, and the installer's workmanship warranty.
• Exclusions, stated plainly.

What questions should you ask before you sign?

1. How did you decide on this size for my house?
2. What is the AHRI certified reference number for this combination?
3. Which refrigerant does it use, and will my line set be reused?
4. Did you inspect my ducts and return air, and what did you find?
5. Is the permit included, and who handles the inspections?
6. Who registers the equipment, and what are the warranty terms?
7. How long will installation take, and what happens if you find a problem once the old system is out?

A contractor who answers these clearly, without pressure to sign the same day, is usually one whose installation matches their quote.

When is the best time to replace an AC in Houston?

Before it fails, if you can. A system that dies in the first heat wave of summer forces a fast decision in a hot house, during the busiest weeks of the year. Replacing on your own schedule, in spring or fall, gives you time to get a load calculation, compare quotes and choose the system you want rather than the one that is available.

Once a new system is in, regular maintenance helps keep it running at its rating and supports the manufacturer's warranty. Ross Air offers HVAC maintenance programs, and starting one from installation day is simpler than catching up later.

How do you compare AC replacement quotes line by line?

Two quotes for a new air conditioner can look alike on the first page and describe very different jobs underneath. Put them side by side and go through them in this order. Where one quote is silent on something the other spells out, ask the silent one to put it in writing before you compare anything else.

Are both quotes for the same size system?

Check the tonnage or the Btu/h capacity on each quote, and ask each contractor how they arrived at it. If one quote is a size larger than the other, find out which one measured the house and which one matched the old unit. The one that measured has a reason you can check.

Is the system certified as a matched set?

Ask each contractor for the AHRI certified reference number for the exact combination quoted. It confirms the outdoor and indoor units have been rated together and shows the SEER2 rating that combination actually achieves. If a quote cannot give you one, it may be pairing a new outdoor unit with an indoor coil that was never rated with it.

What is included, and what is excluded?

Look for the line set, the pad, the drain pan and float switch, the electrical disconnect, the thermostat, the permit, removal of the old equipment and refrigerant recovery. Exclusions matter as much as inclusions. A short quote is not a better one if the missing items turn up later as change orders.

What are the warranty terms, in writing?

Compare the manufacturer's parts warranty, whether it depends on registration and who registers it, and the installer's own workmanship warranty and how long it lasts. They are two separate promises from two separate companies.

If your system is old, needed a major repair or never keeps the house cool and dry, the next step is a proper look at the house, not a guess over the phone. Schedule an in-home replacement estimate with Ross Air and you will get the system sized, the options explained and the job written down before you decide.

Call Ross Air: (281) 223-1176