Heat pump, gas furnace or both: choosing how to heat a Dallas-area home

The answer depends on three things about your house

For most homes in the Dallas area, either a heat pump or a gas furnace can keep the house warm. The better choice depends on whether you have gas service, how you weigh operating cost against upfront cost, and how much the few hard-freeze days each winter matter to you. A heat pump heats and cools with one outdoor unit and moves heat instead of burning fuel. A gas furnace delivers hotter air and keeps its full output no matter how cold it gets. Many homeowners split the difference with a dual-fuel system that runs the heat pump most of the year and switches to the furnace on the coldest days.

I am Brandon Quigley of Quigley Heating & Air in Farmers Branch. Our family has installed and serviced gas furnaces, heat pumps and dual-fuel systems since 1945, and we install Lennox and Trane equipment of all three kinds, so I do not have a favorite to sell you. Here is how they differ and how to decide for your own house.

How each system makes heat

A gas furnace burns natural gas in a sealed chamber, passes the heat through a heat exchanger, and a blower pushes air across it and through your ducts. The combustion gases go out a vent pipe. In summer, the furnace's blower moves air across a separate air conditioning coil.

A heat pump is essentially an air conditioner that can run in reverse. In summer it pulls heat out of the house and releases it outside. In winter it extracts heat from the outdoor air, even cold air, and moves it inside. Because it moves heat rather than creating it, a heat pump can deliver more heat energy than the electricity it uses. ENERGY STAR says a certified air-source heat pump can deliver up to three times more heat energy to a home than the electrical energy it consumes. When the heat pump cannot keep up, electric heat strips in the indoor air handler add warmth, at a much higher operating cost.

Either way, the indoor and outdoor parts have to be matched and sized together. A new heat pump connected to an old, mismatched indoor coil, or a new furnace feeding undersized ducts, will not deliver what the brochure promises. The equipment choice matters, but the installation decides how well it works.

Where a heat pump earns its keep

Our climate suits heat pumps. Winters are mostly mild, and on a typical cool day a heat pump heats efficiently without burning anything. ENERGY STAR notes that heat pumps avoid combustion, so they produce no direct emissions such as carbon monoxide inside the equipment. One outdoor unit handles both seasons, which is simpler than a furnace plus a separate air conditioner, and the cooling side is a full air conditioner in its own right for our long summers.

Heat pumps also make sense where there is no gas service, in additions and in rooms the main system does not reach. Ductless heat pump systems work room by room without ductwork, and cold-climate ductless models are designed to operate at temperatures as low as 5 degrees Fahrenheit. The tradeoff is the feel of the air. A heat pump delivers a steady stream of moderately warm air rather than the hot blast of a furnace, and some people miss that.

Heat pumps also prefer steady thermostat settings. A deep overnight setback can make the system call on its expensive heat strips to recover in the morning, which erases the savings. A thermostat designed for heat pumps, set up correctly, avoids that, and it is one of the details we check when we install one.

Where a gas furnace still makes sense

A gas furnace's output does not drop as the outdoor temperature falls. On a night in the teens, it puts out the same heat it does at 45 degrees, and the air at the vents feels hot. If your house already has gas service, a good flue and a furnace in the closet or attic, replacing it with another furnace is straightforward. ENERGY STAR says a certified furnace is about 15 percent more efficient than a conventional one, so a newer high-efficiency model can also lower the gas bill.

The responsibility that comes with gas is safety. The EPA lists leaking furnaces and back-drafting among the household sources of carbon monoxide, and recommends a professional inspection and tune-up of the central heating system every year. That is a small price, but it is a real one, and it is why every gas home should have working carbon monoxide alarms. My guide to furnace and heat pump warning signs covers what to watch for each fall.

Dual fuel: letting each one do what it does best

A dual-fuel system pairs an air-source heat pump with a high-efficiency gas furnace. The heat pump runs most of the year, handling cooling in summer and heating on mild winter days. When the temperature drops below freezing, where a heat pump starts to struggle, the gas furnace takes over. The switch point is set at the thermostat or a control system, so it happens without you thinking about it.

In our experience, most dual-fuel homes heat with the heat pump for most of the winter, which lowers heating bills, and still have the hot, steady output of gas on the coldest nights. ENERGY STAR makes the same point about heat pumps generally: pairing one with a backup heat source is most efficient when temperatures get low. Dual fuel costs somewhat more to install than either system alone, and it only makes sense if you have gas service. For many households with an aging furnace and an aging air conditioner, it is the option I would look at first.

There is a resilience benefit too. If one half of a dual-fuel system needs a repair in the middle of winter, the other half can often carry the house until the part arrives, which is not true of a heat pump with heat strips alone.

Side by side

No single list fits every house, but these are the differences that come up in almost every conversation we have about replacing a heating system.

Maintenance differs as well. A heat pump runs in both seasons, so its outdoor unit works more hours in a year than an air conditioner does. A gas furnace needs its combustion and safety checks every fall. Our Q Club heating visits cover both, checking heat pump operation including the heat strips, and running a carbon monoxide test on gas equipment.

• Heat pump: heats and cools with one outdoor unit; no gas needed; efficient on mild days; relies on heat strips on the coldest days
• Gas furnace: hot air and full output in any cold; needs gas service and venting; pairs with a separate air conditioner; annual safety inspection matters
• Dual fuel: heat pump most of the year, gas on freezing days; lower heating bills than electric backup; somewhat higher installation cost
• Ductless heat pump: room-by-room heating and cooling where there are no ducts; cold-climate models work to 5 degrees Fahrenheit
• All of them: depend on correct sizing, sound ductwork and regular maintenance to perform as rated

The February question: what happens in a hard freeze

Anyone who lived through February 2021 asks what each system does in a hard freeze, and it is a fair question. Here is the honest answer. In a hard freeze, a standard heat pump leans on its electric heat strips, which keep the house warm but draw a lot of power. A gas furnace keeps putting out full heat. A dual-fuel system switches to gas automatically. ENERGY STAR certified heat pumps are tested for low-temperature performance down to 5 degrees Fahrenheit, and newer cold-climate equipment handles cold far better than the heat pumps many people remember.

There is one thing no forced-air system can do, and that is run without electricity. A gas furnace still needs power for its igniter, controls and blower. If the grid goes down, the choice between gas and a heat pump does not keep the house warm, so plan for outages separately from the choice of equipment.

Questions that settle it for your house

When we sit down with a homeowner, these are the questions that usually decide it. Answer them honestly and the choice tends to make itself. If cost is the deciding factor, my guide on what drives the price of a new system explains how each choice shows up on an estimate.

• Is there gas service at the house, and a sound flue for a furnace?
• How old are the furnace and the air conditioner, and are both due?
• Do the ducts reach every room well, or are there problem areas?
• Does anyone in the house strongly prefer hot air from the vents?
• How long do you plan to stay in the house?
• How do your gas and electric bills compare over a winter?

How we help you choose

Our comfort consultant comes to the house, looks at the existing equipment, the gas service, the ducts and the rooms that bother you, and prepares a tiered estimate with clear options. Where it makes sense, that estimate shows a heat pump, a gas furnace with air conditioning and a dual-fuel system side by side, from Lennox and Trane, including our top recommendation of high-efficiency variable-speed equipment. Wells Fargo financing is available with approved credit.

If you go ahead, installation is usually completed in under a day, and I explain what to expect in my guide to replacement day. We serve homes across Dallas, Farmers Branch, Carrollton, Coppell, Frisco, Garland, Highland Park, Plano, Richardson and University Park, and we service every brand, so whichever system you choose, we can keep it running.

Questions people ask me