Yes. A properly sized heat pump heats a Houston home through a normal freeze, and it keeps working below 32 degrees. Somewhere in the 30s, depending on the house, the electric auxiliary heat stages in automatically to make up the difference. The February 2021 failure was the power grid, not the equipment: heat pumps, furnaces and everything else stopped when the electricity did. On January 16, 2024, when Bush Intercontinental Airport hit 19 degrees, a record low for the date, the problems were backup heat that did not stage in, thermostats set wrong, and attic ducts leaking heat, not heat pumps that could not make heat.
Houston's average first freeze lands around December 9. That leaves a couple of months to read this, check the system and fix what needs fixing before the first cold night, when every HVAC company in the area is booked.
A heat pump does not create heat; it moves it. Even at 30 degrees the outdoor air holds heat energy, and the refrigerant in the outdoor coil is colder than the air, so heat flows into the refrigerant, the compressor concentrates it, and the indoor coil releases it into the house. The colder it gets outside, the less heat there is to move and the harder the compressor works, so capacity falls as the temperature drops. Modern variable-capacity units hold useful output well into the 20s.
The Gulf Coast consequence is the part most national articles miss. Houston has a few hundred heating hours a year and a few thousand cooling hours, so the cooling load sets the equipment size. A heat pump sized correctly for August has more heating capacity than the house needs on almost every winter night, which is why heating capacity is rarely the constraint here. Sizing matters in the other direction: an oversized unit short-cycles all summer and never dehumidifies the house properly. Our Manual J sizing guide explains how both loads get calculated.
Auxiliary heat (AUX on the thermostat) is the electric resistance strip heater inside the air handler. The thermostat turns it on automatically when the heat pump alone cannot keep up: when the house is more than a couple of degrees below the setpoint, when the outdoor temperature drops below the balance point programmed for the house, or during a defrost cycle so the supply air does not blow cold. The heat pump keeps running underneath it. AUX is normal, and on a 25 degree night you should expect to see it.
Emergency heat (EM HEAT) is a manual switch that turns the heat pump off and runs the strips alone. It exists for one situation: the heat pump has failed and you need heat until it is repaired. Strip heat draws several times the power of the heat pump for the same warmth. Running it for hours because someone flipped the switch "to be safe" before a freeze is the bill spike that gets blamed on the heat pump every February. If the AUX indicator is on constantly and the house still will not warm up, that is a service call, not a reason to switch to EM HEAT.
A dual-fuel system pairs a heat pump with a gas furnace instead of electric strips. The heat pump carries mild days at high efficiency, and the control hands off to the furnace automatically when the outdoor temperature drops below a set point, so the furnace does the cold-night work at high supply temperatures. The homeowner who should consider it already has a gas line and a working furnace in the attic and is replacing the air conditioner: adding a heat pump outdoor unit in place of a straight-cool condenser turns the existing furnace into the backup. We service and install dual-fuel systems across the area; see our furnace services page for the furnace side. For a home with no gas line, a heat pump with electric auxiliary heat is the normal and correct setup.
HSPF2 is the heating-season efficiency rating for heat pumps, the winter counterpart to SEER2, measured under the test procedure adopted in 2023. A higher number means more heat per kilowatt-hour across a typical heating season. In Houston it matters less than SEER2 because the heating season is short; the unit spends most of its life cooling, so the cooling rating drives the operating cost. Buy the SEER2 you need, confirm the HSPF2 is respectable, and put the remaining budget into the ductwork.
The median home in Deer Park was built in 1982, and the housing stock in Pasadena and La Porte is from the same era: single-story slab ranch homes with the air handler and every duct run in a vented attic. On a 20 degree night that attic is close to 20 degrees, and a 40-year-old duct system leaks conditioned air into it at the seams, at the boots, and where the flex duct has sagged and crushed. The heat pump makes the heat; the ductwork gives a share of it to the attic before it reaches a register. Undersized returns make it worse by starving airflow across the indoor coil, which drops the supply temperature and triggers auxiliary heat sooner than it should.
That is a building-science problem with a measurement. A blower door quantifies how leaky the house is, and a TrueFlow Grid measures the actual airflow the system delivers against what it was designed for. Together they show whether the fix is sealing the ducts, adding a return, insulating the attic, or, occasionally, the equipment. This is the same testing we run before sizing a replacement, and it is the reason two identical heat pumps on the same street can perform so differently on the same cold night.
Once the weather breaks, walk the system. If the AUX indicator on the thermostat is still lit with the outdoor temperature back in the 50s, the heat pump is not carrying the load and something is wrong. If the first bill after the freeze is far higher than the same period last year, look at duct leakage and thermostat setbacks before blaming the equipment. Outside, confirm the fan spins when the unit runs, that the coil is free of ice, and that nothing is bent or leaning. Inside, check for water around the air handler; a frozen or cracked condensate line shows up here. Any of those is a same-day service call for our heat pump repair team across Deer Park, La Porte and Pasadena.
Thinking about a heat pump, or replacing one that struggled last winter? Start with heat pump installation and repair or our general heating services. Already have a gas furnace and want the dual-fuel setup? See furnace services. Before you buy, check which utility incentive applies to your address in our guide to AC and heat pump rebates by utility. Or call 281-402-5100. Texcellent is licensed under TACLA77699C.
A: No. Emergency heat (EM HEAT on the thermostat) shuts the heat pump off and runs the electric strip heaters alone. It exists for a heat pump that has failed, not for cold weather. Leave the thermostat in normal heat mode and the system will stage auxiliary heat in by itself when the heat pump needs help. Switching to emergency heat ahead of a freeze only guarantees the most expensive kind of heating for the whole event.
A: That is a defrost cycle. In cold, damp air the outdoor coil frosts over, so the unit briefly runs in cooling mode to melt the frost, and the melt flashes to steam when it hits the warm coil. The outdoor fan stops, the indoor air may feel cool for a few minutes, and then normal heating resumes. Steam and a puddle under the unit are normal. Ice that never clears, or a defrost that repeats every few minutes, is a service call.
A: Electric strip heat. Auxiliary heat draws several times the power of the heat pump for the same warmth, and it runs whenever the house is more than a couple of degrees below the setpoint or the outdoor temperature drops below the balance point. A big thermostat setback, a low outdoor temperature, and a leaky attic duct system can keep the strips on for hours. That is the bill spike, and it is a sign to check the ductwork and the thermostat settings, not to replace the heat pump.
A: Most homes do not. Houston averages a handful of freezing nights a year, and a properly sized heat pump with electric auxiliary heat covers them. A dual-fuel setup (heat pump plus gas furnace) makes sense when the house already has a gas furnace in good shape, when the home is large or leaky enough that strip heat would run for long stretches, or when you want heat that does not depend on the electric grid staying up. The furnace still needs power for its blower and controls, so it is not a full outage solution either.
A: On the Gulf Coast, almost always. A Manual J load calculation figures both loads, and in Deer Park the cooling load is the larger of the two by a wide margin, so the equipment that handles August has capacity to spare on a 30 degree night. The exception is a house with heavy duct leakage or very little insulation, where heating capacity leaks into the attic faster than the unit can supply it. That is a building fix, not a bigger heat pump.