How a Heat Pump Works — and Why It Fits Houston's Climate

Published October 16, 2026 · Reviewed October 16, 2026

Part of our Heat Pump Services guides.

What is a heat pump?

A heat pump is an electric system that heats and cools your home by moving heat rather than making it. In summer it works exactly like a central air conditioner, pulling heat out of your house and releasing it outdoors. In winter it runs in reverse, collecting heat from the outdoor air and releasing it indoors.

From the curb, a heat pump looks like an ordinary outdoor AC unit. Inside, the key difference is a component called the reversing valve, which switches the direction the refrigerant flows. That one part lets a single system replace both an air conditioner and a furnace.

A heat pump is an air conditioner that can also run backwards to heat your home.

How does a heat pump move heat?

A heat pump moves heat by circulating refrigerant between an indoor coil and an outdoor coil, letting it absorb heat in one place and release it in the other. The cycle has four main parts:

1. Evaporating coil. Cold, low-pressure refrigerant absorbs heat from the air passing over it. In cooling mode this is the indoor coil; in heating mode it is the outdoor coil.
2. Compressor. The compressor in the outdoor unit squeezes the refrigerant vapor, raising its pressure and temperature.
3. Condensing coil. The hot refrigerant releases its heat to the air passing over this coil. In cooling mode that is outdoors; in heating mode it is the indoor coil, warming the air your blower sends through the ducts.
4. Expansion device. The refrigerant drops in pressure and temperature, ready to absorb heat again.

The reversing valve decides which coil plays which role. Even air that feels cold to you still contains heat that refrigerant colder than that air can absorb, which is why a heat pump can heat a home on a cool day.

Two heating-mode features worth knowing

• Defrost mode. In heating mode the outdoor coil gets cold enough that frost can form on humid winter days. The system periodically switches briefly to cooling mode to melt it. You may see steam rising from the outdoor unit and feel cooler air indoors for a few minutes; this is normal.
• Auxiliary (backup) heat. Most heat pumps have electric heat strips in the indoor air handler that help on the coldest mornings or during defrost. They work like a toaster coil and use far more electricity than the heat pump itself, so frequent use is worth noticing.

Why does a heat pump fit Houston's climate?

A heat pump fits Houston because the region needs far more cooling than heating, and a heat pump's heating side only has to cover a short, mild winter. NOAA's 1991–2020 normals for Houston Intercontinental Airport show about 3,288 cooling degree days a year against 1,266 heating degree days, roughly 2.6 times as much cooling demand as heating demand. The same normals show about 111 days a year at or above 90°F, with normal daily highs of 94.5°F in July and 94.9°F in August.

In practice, that means:

• The cooling side does most of the work. A heat pump's cooling performance, rated in SEER2, matters most for a Houston household's year-round comfort and electric bills.
• The heating side runs in conditions it handles well. Most Greater Houston winter days are mild, which is when air-source heat pumps work most efficiently.
• One system covers both seasons. There is no separate furnace to maintain, and homes without natural gas service do not need it for heat.

Every new split-system heat pump sold in Texas must meet at least 14.3 SEER2 for cooling and 7.5 HSPF2 for heating under DOE's 2023 standards.

When is a heat pump not the best fit?

A heat pump is not automatically the best choice for every Houston home; a few situations call for a closer look. During the rare hard freeze, a heat pump leans on its backup heat, which uses much more electricity just when cold weather is driving up electricity use across the region. Homes that already have gas service and a working furnace may find that keeping the furnace and pairing it with a heat pump or an AC makes more sense. Ductwork in poor condition will hold back any new system.

The right answer depends on your utility rates, your existing equipment and how you use your home, which is why the comparison is worth running with your own numbers.

What commonly goes wrong with heat pumps?

Most heat pump problems trace back to airflow, the outdoor coil, the defrost cycle or the reversing valve. Common signs and what they can mean:

• Cool air in heat mode. Often a normal defrost cycle; if it continues, the cause may be the thermostat setting, the reversing valve or low refrigerant.
• Ice that stays on the outdoor unit. Light frost that clears during defrost is normal; a thick block of ice is not.
• High winter electric bills. Backup heat may be running more than it should.
• Weak airflow in either season. A dirty filter, blocked return or dirty indoor coil restricts the air the system depends on.
• Debris around the outdoor unit. Leaves, grass clippings and fencing too close to the coil reduce heat transfer.

What can a homeowner safely check?

A homeowner can safely check the thermostat, the air filter, the breaker and the area around the outdoor unit; anything involving refrigerant, electrical components or the reversing valve needs a licensed technician.

Safe checks:

1. Thermostat. Confirm it is set to the right mode (Heat, Cool or Auto), the setpoint is where you want it and the display has power. Note whether an "Aux" or "Em Heat" indicator is lit.
2. Air filter. Replace it if it looks gray or clogged.
3. Breakers. Check the breakers for the indoor and outdoor units. If a breaker trips again after one reset, leave it off and call a technician.
4. Outdoor unit. Clear leaves and debris from around it and keep plants trimmed back. Do not chip ice off the coil.
5. Condensate drain. In cooling season, check that the drain line is not backing up; see our blog post on how to fix a clogged AC drain line.

Leave to a technician: refrigerant checks and leak repair, capacitors and contactors, defrost controls, the reversing valve and the backup heat strips.

Most "my heat pump is blowing cold air" calls in mild weather start with the thermostat or a normal defrost cycle.

What should you do if you are considering a heat pump?

If you are considering a heat pump, start by comparing its operating cost against an AC and gas furnace using your own electricity and gas rates, then look at the equipment ratings and the condition of your ductwork. Questions to bring to any quote:

• What are the certified SEER2 and HSPF2 ratings of the matched indoor and outdoor units?
• How is backup heat sized and controlled?
• Has a load calculation been done for your home?
• Which refrigerant does the system use?

JHC Cooling & Heating installs and services Goodman equipment, including heat pumps, across Greater Houston.

Frequently Asked Questions

Does a heat pump work in Houston winters?

Yes. Houston winters are short and mostly mild, which suits an air-source heat pump. NOAA's 1991–2020 normals for Houston Intercontinental Airport show about 1,266 heating degree days a year compared with about 3,288 cooling degree days.

Is a heat pump the same as an air conditioner?

In cooling mode, yes: a heat pump cools exactly like a central air conditioner. The difference is a reversing valve that lets it also run in reverse to heat your home, so one system handles both seasons.

Why is steam coming off my heat pump in winter?

That is usually the defrost cycle melting frost from the outdoor coil. The system briefly switches to cooling mode to do this, and the steam and short burst of cooler indoor air are normal.

What is auxiliary or emergency heat on a heat pump?

Auxiliary heat is usually a set of electric heat strips in the indoor air handler that supplement the heat pump on the coldest days or during defrost. It uses much more electricity than the heat pump itself, so if it runs often in mild weather, have the system checked.

What efficiency does a new heat pump need in Texas?

A new split-system heat pump must be rated at least 14.3 SEER2 for cooling and 7.5 HSPF2 for heating under DOE's 2023 efficiency standards.

Can I fix a heat pump that is not heating myself?

You can safely check the thermostat mode and setpoint, replace a dirty filter, check the breakers once and clear debris from the outdoor unit. Refrigerant, electrical components, defrost controls and the reversing valve need a licensed technician.

Sources

1. NOAA NCEI, U.S. Climate Normals 1991–2020, Houston Intercontinental Airport (USW00012960) — cooling and heating degree days, days at or above 90°F, July and August normal highs (as of October 16, 2026)
2. eCFR, 10 CFR 430.32 — Energy and water conservation standards — minimum efficiency for split-system heat pumps (as of October 16, 2026)
3. U.S. Department of Energy, 2023 Central Air Conditioner and Heat Pump Standards FAQ (October 5, 2022) — SEER2 and HSPF2 metrics (as of October 16, 2026)