SAN ANTONIO GUIDE

What a heat pump is doing most of the year

The outdoor unit runs on a mild evening, the supply air is warm but not hot, and someone wonders whether the heat is broken because the flame never lit. On a heat pump there may be no flame. The same machine that spent the long cooling season moving heat out of the house reverses and moves heat in. San Antonio winters are usually mild enough for that to cover a lot of the heating. The attic air handler, the condensate drain, and the outdoor coil still do the summer work that actually fills the calendar.

By Mike Maziarz · Sources checked October 6, 2026 · How we write these guides

Cooling first, heat as the reverse

In cooling mode a heat pump is an air conditioner. The indoor coil absorbs heat, the outdoor coil dumps it, and condensate has to leave the attic or the closet the whole time the system runs. That is the mode that matters from late spring through a long fall. Judging the machine only by how it behaves on a January night misses the work it does for most of its hours.

In heating mode the refrigerant circuit flips. The outdoor coil becomes the cold coil, even on a day that feels only chilly, and the indoor coil becomes the warm one. Supply air is often milder than the air from a gas furnace. People who grew up with scorching registers sometimes call that weak heat. It can still hold the house if the system is keeping up with the thermostat. Ask whether the temperature is rising, not whether the air feels like a furnace.

Auxiliary strips and emergency heat

Electric heat strips in the air handler are the backup, sometimes called auxiliary heat. They come on when the heat pump cannot close the gap alone, during a defrost, or when the outdoor unit is locked out. On an ordinary San Antonio night they may never run. On a colder night you might see the thermostat say auxiliary while the strips add heat. That is different from emergency heat, a manual setting that forces the strips and keeps the compressor off.

Emergency heat is for a failed outdoor unit, not for every front that drops into the forties. Left on, it skips the heat pump entirely and heats with electricity alone. Switch it back once the outdoor unit is working, and tell the technician if someone turned it on because the house would not warm. A breaker for the heat kit, a sequencer, or a thermostat that was configured for the wrong system can all leave you with strips that never come on or strips that never turn off. Those are measurements, not a new thermostat bought on the way home.

Steam, a pause, and the defrost cycle

The outdoor coil ices when it is the cold coil in heating mode. The system defrosts by briefly reversing, which melts that ice. You may see steam, hear a rush, and feel the indoor supply air cool for a few minutes while strips, if they are working, try to cover the gap. A defrost that ends and returns to heat is normal. A unit that stays iced, or that steams and then never heats again, is not.

Do not chip ice off the fins, and do not pour hot water through the electrical side of the cabinet. Clear leaves so the coil can breathe, with power confirmed off, and then watch a full call for heat. Note how long the steam lasts and whether the thermostat flashes auxiliary. A stuck reversing valve can leave the system cooling when you asked for heat, or heating when you asked for cooling. That symptom belongs in the notes as the mode you requested versus the air you felt.

Mild winters and the uncommon freeze

Humid subtropical winters here are mild more often than they are severe. A heat pump sized around cooling can carry many of those nights without drama. Hard freezes are uncommon and still real. During the February 2021 freeze, backup heat was the difference between a house that could hold and a house that could not, because the outdoor unit was outside in weather it rarely sees. This page does not tally damage from that event. It does say you should know, before the next front, whether your backup is strips, a gas furnace, or nothing you have ever tested.

Test heat on a mild afternoon. Confirm the thermostat is not sitting in emergency heat from last year. Confirm the outdoor unit actually starts. If the house also has a gas furnace beside a cooling coil, you may not have a heat pump at all. The outdoor cabinet nameplate and the indoor data plate settle that. Limestone under the pad does not change the refrigerant circuit. A tilted pad still matters because it strains the line set, the same way it does for a straight air conditioner.

When the long season is the failure

A heat pump that will not cool in July is an air conditioner failure, with the same attic heat, the same condensate load, and the same risk of a float switch sitting in a full pan. If the house is dangerously hot, older adults, infants, and anyone who already feels ill should not wait out the afternoon. Get them to a cooler place, and call emergency services if someone is in distress. The same-day checklist is in no-cooling emergency steps.

Long cooling runtimes are also how a heat pump pulls moisture out of the air. Short cycles, a fan left on after the coil is wet, or a coil that cannot stay cold leave the house clammy even when the thermostat is close. That side of the complaint is covered in indoor humidity. Say whether the problem is temperature, stickiness, or both, because a technician chasing only the number on the wall can miss a drain or a fan setting.

Parts, permits, and what changes the bill

Replacing an outdoor heat pump, an air handler, or the refrigerant line set is often more than a part swap, and the City of San Antonio Development Services Department or Bexar County may expect a permit depending on the address and the scope. Confirm which office applies instead of assuming a like-for-like box change is invisible to the building department. The permit questions to ask are in permits and inspections. A state contractor license is a separate lookup from that permit.

The bill for a heat pump repair moves with attic access, whether the refrigerant circuit has to be opened, whether strips failed along with the compressor, and whether the call is after dark in August or on a mild weekday. No honest guide can price that from a paragraph. The factors themselves are listed in repair cost factors. Ask the technician which mode they tested, whether defrost completed, and whether auxiliary heat was measured or only described.