From Gas Wall Furnace to Ductless Comfort in Austin

Updated September 2026 · ATX Mini Split King, Austin and Central Texas

That old gas wall or floor furnace got your space through many winters, but Central Texas summers ask a different question. A ductless mini split answers with both efficient cooling and heating from one system. Here is the honest breakdown of what that switch means, when it makes sense, and what the work actually looks like inside your home.

Flat pricing, everything included

Those are materials and labor together, wired to code by a TDLR licensed contractor. Anything non standard gets quoted first, before a single tool comes out of the truck: a very long line set, an electrical panel that needs work, a difficult mount, a roof or masonry penetration, disposal of the old equipment. You hear the number before we start, not after.

What a Ductless Mini Split Actually Is

A ductless mini split is a two part electric heat pump system. An outdoor unit sits on a concrete pad or wall bracket outside your house. One or more slim indoor heads mount high on an interior wall or the ceiling. The two units connect only by a small bundle that passes through a neat hole in the wall. Inside that bundle are two copper refrigerant lines, a slim condensate drain tube, and the communication wire. There are no ducts anywhere in the system.

In cooling mode, the outdoor unit extracts heat from indoor air and dumps it outside, exactly like a central air conditioner works but without the ductwork. In heating mode, the cycle reverses. The outdoor unit pulls heat energy from the outside air, even on chilly Austin winter days, and moves it indoors. Because electricity moves the heat rather than creating it from scratch, the system delivers three to four units of heat output for every unit of electricity it draws. It is fundamentally different from a gas furnace that burns fuel to make heat.

Each indoor head runs independently. The homeowner sets the temperature room by room using a wireless remote. Some systems connect to phone apps or wall mounted thermostats. In a smaller home or an addition, one outdoor unit paired with a single indoor head handles both heating and cooling duties for that zone. A larger home might have one outdoor unit serving two or three indoor heads in different rooms. This is the core of the replacement path for an old wall or floor furnace that only blew hot air into one or two adjoining spaces.

Real Pros of a Wall or Floor Furnace

Let us be fair to the old equipment. A standing gas wall or floor furnace does a few things honestly well. It makes strong, fast heat. On a cold January morning in a pier and beam house, that radiant warmth feels immediate. The furnace itself is simple hardware. The gas valve, the thermocouple, the burner, and the heat exchanger have no circuit boards, no inverters, no refrigerant pressures to manage. This mechanical simplicity means a skilled technician can often diagnose and repair one quickly with basic parts.

The footprint matters too. A wall furnace sits inside its own slim sheet metal cabinet recessed between wall studs. A floor furnace lives entirely below floor level with just a flush grate visible. Neither one eats any square footage, blocks a window, or interrupts furniture placement the way a wall mounted mini split head will. For decades, builders put these in small postwar houses, garage apartments, and room additions precisely because they took almost no floor or wall real estate.

There is also a fuel cost reality. Natural gas in Central Texas has historically been inexpensive per unit of heat delivered. In a short, mild winter like ours, the total annual cost to run the wall furnace may be lower than the electrical cost of a heat pump for those same few weeks. If your existing furnace runs safely and your cooling arrangement is already handled, the money you might save by switching may take a long time to offset the upfront installation cost.

Honest Cons and Limits of That Old Furnace

The biggest and most honest drawback is the one Austin homeowners feel hardest: the wall furnace does nothing for you from April through October. Zero cooling, zero dehumidification. Austin regularly sees ninety plus days above ninety degrees. A home with only a gas wall furnace and no separate air conditioning system, or with a pair of loud window units, stays hot and sticky for half the year. The furnace is a one season appliance in a two season climate.

Efficiency and air comfort are another honest limitation. A natural draft furnace pulls combustion air from the room it sits in and sends warm air and combustion byproducts up a metal flue through the roof. Much of the heat goes out that flue. The indoor airflow is uneven, hot near the grate, cool near the walls. There is no real filtration. Dust, pollen, and pet dander recirculate with no meaningful capture. A wall furnace with an open pilot light can also add noticeable heat to the room during summer, working against any window air conditioner you are trying to run.

Safety considerations move from nuisance to genuine hazard over a long enough timeline. A cracked heat exchanger can allow combustion gases into the living space. A rusted out flue pipe can vent carbon monoxide into the attic instead of outdoors. A floor furnace grate gets hot enough to burn small feet. Older gas valves and connectors can develop slow leaks. These are not design flaws of one brand. They are age sensitive risks shared by every decades old gas appliance with a flame inside the house. The system deserves honest respect and regular professional inspection.

Signs That the Wall or Floor Furnace Is Near Its End

Visible rust and corrosion tell the first story you do not need a tool to read. Surface rust on the cabinet is cosmetic. Rust on the burner, on the heat exchanger seams, or around the flue connection is structural. If you see white powdery deposits or brown flaking metal inside the burner compartment, water and combustion gases have been reacting with the steel for years. A floor furnace sitting in a damp crawlspace often rusts through from below long before you see damage from above.

Unusual flame behavior is the next unmistakable sign. The burner flame should be steady and blue with small yellow tips. A lazy, mostly yellow, or floating, lifting flame that dances around means poor combustion. This can come from a cracked heat exchanger, a rust plugged burner orifice, or a weakening gas regulator. Soot build up on the interior walls of the cabinet or black streaks around the ceiling grate are evidence that combustion is no longer clean. The smell of aldehydes, a sharp, unpleasant odor distinct from the normal brief smell at startup, deserves an immediate no heat call and a serious conversation about replacement.

The subtler signs are repeated repairs and creeping discomfort. A gas valve replacement, a thermocouple change, limit switch fixes. One repair after another on a furnace past twenty years old is real money going into a machine that still cannot cool your house. The rooms may also feel cooler even when the furnace runs because air leaks around the old wall opening, the flue joint, or through a rust perforation in the floor pan are stealing conditioned air from the room before you ever feel it.

What the Mini Split Replacement Job Involves

The work begins with the removal. Our crew shuts off the gas supply at the appliance isolation valve, disconnects and caps the gas line, and removes the old furnace entirely. For a wall furnace, that means pulling the sheet metal cabinet out of the stud bay. For a floor furnace, the grate, firebox, and underfloor enclosure come out. The metal flue pipe running through the attic or roof space gets removed in sections. The roof penetration gets a permanent metal patch and a weather tight seal. The old gas stub out in the wall or floor is capped with a threaded steel fitting, leak tested, and left secure inside an accessible box or access panel.

The wall patch is specific to the furnace type. A wall furnace leaves a rectangular opening roughly fourteen inches wide and two or three feet tall between two studs. We frame in the opening, insulate the cavity, hang drywall, tape, float, and texture to match the surrounding wall as closely as the age and paint allow. A floor furnace leaves a much larger rectangle cut through floor joists. We sister framing to the existing joists, lay plywood subfloor, and install finish flooring to match what the room has. The goal is a patch that looks like a repair, not a showroom miracle. You will know something was there, but the hole will be closed, insulated, and solid.

The mini split installation happens on the same day or a coordinated next day. One or more indoor heads mount on exterior walls. A single hole, roughly three inches, passes the line set, drain, and control wire directly through the wall behind the head. The outdoor unit sits at ground level or on a wall bracket outside. The electrical work runs from the outdoor unit to a new dedicated circuit in the main panel, using a disconnect box near the unit. Condensate drains by gravity to the outside, downhill from the wall penetration. The whole crew works as one TDLR licensed HVAC and electrical contractor. Standard jobs with one indoor head are $1,500 complete, materials and labor included. Two heads are $2,500. Three heads are $3,500. Those prices assume standard back to back mounting, a straightforward electrical path, and a panel with space for a new breaker. Anything nonstandard, long line sets, a panel upgrade, a complicated wall bracket, an awkward crawl, gets quoted in plain writing before we touch the house.

When Switching Is the Wrong Move Right Now

If your wall or floor furnace is less than fifteen years old, runs with a clean blue flame, has no rust or soot, and you already cool the space with a reasonably efficient central air conditioner or ducted heat pump you are happy with, do not tear out a working furnace just to change technologies. The honest path is to maintain what you have, have a licensed technician inspect it every other year, and keep your dollars. Switching makes sense when the furnace has failed or when cooling is the driving need. Switching just because the mini split is newer technology is an expensive way to solve a problem you do not have.

A home with an extensive intact duct system that just needs a modern central heat pump is another case where a ductless mini split may be the wrong tool. If your ducts are in decent shape, sealed, insulated, and sized correctly, a single ducted system can condition every room more uniformly and more cleanly than a few scattered ductless heads. The mini split shines in a ductless house, an addition, a converted garage, a small apartment, or a space where the old wall furnace was the only heating and the only cooling was a window unit. That is its sweet spot. A whole house with functional ducts is often better served by a ducted inverter heat pump, which we can also talk through honestly.

Finally, a simple repair and a short wait can be the smartest call. If it is October and your wall furnace has a bad thermocouple, a sixty dollar part and a service call get you through a winter you will barely use the heat after March. That buys you months to plan, save, and schedule replacement work during the mild spring or fall when you do not need heating or cooling. A cracked heat exchanger or a gas leak is different. That is a hard stop. But a worn small part on an otherwise sound furnace in a home that already has good cooling is not an emergency. You have our honest blessing to repair it, run it, and only call us when the situation changes.

Questions people actually ask

Will the wall patch after removing a wall furnace be invisible?

We match texture and paint as closely as possible, but no patch is completely invisible. The existing wall has aged paint that has faded, picked up scuffs, and soaked in years of dust and cooking oils. Fresh paint, even perfectly matched, sits differently on the wall. The patch will be smooth, solid, and insulated, painted the same color. It will look like a proper repair. The alternative is painting the entire wall, which you can choose to do separately after our work is complete.

What happens to the gas line after the furnace is removed?

We shut off the gas at the appliance valve nearest the furnace, disconnect and cap the branch line, and leave the capped stub securely inside a flush access plate in the wall or floor. The gas line is not routed outside. It remains inside the building envelope, sealed, leak tested with soap solution, and completely inert. If you later want a gas appliance elsewhere, the stub can be extended. If you never want gas again, the line is safely dead ended.

Can the mini split really heat well on those rare freezing Austin nights?

Yes. A modern inverter heat pump pulls usable heat from outdoor air even when the temperature drops into the teens. The system does not stop producing heat. It will continue to run and deliver warm indoor air. In extremely cold conditions, the output capacity reduces somewhat, but Austin extremely cold means a handful of nights near twenty degrees, not a week at ten below. The system handles our climate without a backup heating source in the vast majority of homes.

Does each indoor head need its own outdoor unit?

Not necessarily. A single outdoor unit can serve two or three indoor heads in different rooms. This arrangement is called a multi zone system. The outdoor unit sizes up appropriately. Each indoor head still operates independently. You can set the bedroom to seventy two and the living room to sixty eight. The outdoor unit modulates its output to match the combined demand from the heads that are calling. Our standard flat pricing covers one, two, and three head configurations.

What if my electrical panel is full or very old?

A mini split needs a dedicated circuit with its own breaker. If your panel has no space for a new double pole breaker, we can sometimes add a slim breaker where code allows. If that is not possible, or if the panel is a dated model with known safety issues, a panel upgrade or subpanel addition becomes part of the job. That work falls outside the standard flat pricing. We inspect the panel during the initial visit and give you a firm quote for any electrical work before you commit.

Keep reading

Every replacement guide we have written is listed on the replacement guide hub. Next door to this page: replacing a gas pack all in one heating and cooling unit with a ductless mini split, replacing a ducted central heat pump with a ductless mini split. Pricing, service area and the quote form all live on the ATX Mini Split King home page, and the Austin mini split cost guide covers what the rest of the market charges.