Heat Pumps in a Houston Winter: How They Work and What Goes Wrong
Heat pumps are the most common heating system in newer Houston homes, and they are a good match for our climate: they move heat instead of making it, so they heat efficiently on all but the coldest nights of the year. But they work very differently from a gas furnace, and the faults that show up in winter — icing, defrost problems, auxiliary heat running nonstop — confuse a lot of homeowners. Here is how your heat pump handles a Houston winter, and what to watch for.
How a Heat Pump Heats
A heat pump in heating mode pulls heat from the outside air — even cold air contains heat energy — and moves it indoors through refrigerant. It does not burn fuel, so there is no flame, no gas, and no carbon monoxide risk from the heating itself. In Houston, where winter lows are usually in the 40s and 50s, a heat pump can heat a home comfortably while using far less electricity than electric resistance heat.
The Defrost Cycle, Explained
In heating mode the outdoor coil gets cold enough to ice up, so the system periodically reverses itself for a few minutes to melt the frost off. During defrost you may see steam rising from the outdoor unit and hear the reversing valve shift — both are normal. What is not normal is ice that never melts, or a unit that stays iced over for days. That points to a failed defrost sensor, control board, or reversing valve.
Auxiliary Heat: Backup, Not the Main System
On the coldest nights, electric auxiliary heat strips kick in to help the heat pump keep up. They are meant to run briefly. If your auxiliary heat runs for hours on a mild night, or your electric bill suddenly doubles in January, the heat pump itself is probably not doing its job — often because of low refrigerant, a dirty coil, or a failing compressor. A technician can test this in one visit.
Why Houston Winters Suit Heat Pumps
Heat pumps lose efficiency as the outside temperature falls, but Houston rarely gets cold enough for that to matter much. Most winter nights stay well within the range where a heat pump heats efficiently, which is why so many Houston builders install them. The trade-off is that the same system also cools your home all summer, so it accumulates twice the running hours of a furnace-only system and needs regular maintenance.
Common Winter Faults
The faults we see most in winter are a reversing valve stuck in cooling mode, a failed defrost control, low refrigerant charge, and a dirty outdoor coil choked with leaves. The symptoms overlap — cold air from the vents, constant running, ice on the outdoor unit — so diagnosis with gauges and meters matters more than guessing. Our trucks carry the common parts for Carrier, Trane, Lennox, Rheem, Goodman, American Standard, Amana, and York systems.
Keeping Your Heat Pump Healthy
Clear leaves and debris from around the outdoor unit, keep the filter clean, and book an autumn check of the defrost cycle and refrigerant charge. If ice builds up on the outdoor unit and never melts, switch the system to emergency heat and call us — running a iced-up heat pump can damage the compressor. With basic care, a heat pump is one of the most reliable ways to heat a Houston home.
The Bottom Line
A heat pump is one of the best ways to heat a Houston home — efficient on mild nights, quiet, and safe, with no combustion at all. The problems that do appear in winter are almost always small faults that went unnoticed through the summer: a defrost sensor, a sticking valve, or low refrigerant. An autumn check catches all three before the first cold front. If your outdoor unit stays iced over, your auxiliary heat runs constantly, or the system blows cold air in heating mode, call (281) 549-0799 — our technicians are NATE-certified and the diagnostic is free with the repair.
When a Heat Pump Needs a Professional
Some heat pump behaviour is normal in winter and some is not, and knowing the difference saves you a wasted call or a damaged compressor. Steam during the defrost cycle, a brief reversal sound, and auxiliary heat running for a few minutes on the coldest night are all normal. Ice that never melts, auxiliary heat running for hours, cold air from the vents in heating mode, and a system that runs constantly without reaching the set temperature are not — each points to a fault that will only get worse if left alone. A heat pump that is low on refrigerant, for example, will ice up more and more until the compressor itself is damaged, turning a moderate repair into a major one. If you are unsure, call and describe the symptoms: our dispatch line is answered by a technician, not a call centre, and we can usually tell you over the phone whether it is urgent. The diagnostic is free with any repair, and the visit includes a full check of the defrost cycle, refrigerant charge, and auxiliary heat.
It is also worth watching your electric bill through the first winter month. A healthy heat pump in a Houston winter should cost noticeably less to run than electric resistance heat, and a sudden jump usually means the auxiliary strips are doing work the heat pump should be doing. Compare the bill with the same month last year, allowing for colder weather, and if the increase is large with no obvious explanation, have the system tested. The check is quick — refrigerant charge, coil condition, defrost operation, and auxiliary heat staging — and it often finds a small fault before it becomes a large one. A heat pump that is looked after in autumn will heat your home efficiently all winter, and it will cool it efficiently all summer too.
At a Glance
| Symptom | Likely Cause | What to Do |
|---|---|---|
| Ice on the outdoor unit that never melts | Defrost control failure | Switch to emergency heat and call us |
| Auxiliary heat running constantly | Heat pump not carrying the load | Book a diagnostic — check refrigerant and coil |
| Blowing cold air in heating mode | Reversing valve stuck | Needs a technician; do not keep running it |
| Steam from the outdoor unit | Normal defrost cycle | No action needed if it clears in minutes |
| Electric bill doubled in winter | Aux heat or low charge | Have the system tested before the next bill |
Frequently Asked Questions
Yes — a heat pump can still pull heat from freezing air, and auxiliary heat covers the coldest hours. If the system cannot keep up during a hard freeze, have it checked rather than assuming it is normal.
Steam during the defrost cycle is normal and clears within minutes. Ice that stays on the coil for days is a fault and needs attention.
Auxiliary heat should only run on the coldest nights. If it runs constantly, the heat pump is likely low on refrigerant, has a dirty coil, or has a failing component.
No — covering it traps moisture and blocks airflow. Just keep leaves and debris clear of the unit and let the defrost cycle do its job.
Once a year at minimum, ideally in autumn before the heating season, so defrost, charge, and auxiliary heat are all verified before the first cold front.
Service Area
Same-day heating and AC service across the Houston metro, 24/7. If you need help with your furnace or heat pump, a stocked truck is already nearby.
We dispatch across Houston, TX, including ZIP codes 77002, 77003, 77004, 77005, 77006, 77007, 77008, 77009, 77019, 77027, 77056, 77057, 77063, 77077, 77079, 77080, 77081, 77082, 77084, 77090, 77095, 77098, 77099. Call (281) 549-0799 and we will route the nearest available technician to your door.
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