Why Isn't My Heat Pump Heating When It's Cold Outside?
Most of the time, a heat pump that seems weak in cold weather isn't broken — it's doing exactly what heat pumps do. Defrost cycles, milder supply-air temperatures than a gas furnace, and auxiliary-heat staging all make a healthy system feel like it's struggling during a Rogue Valley cold snap. At Stone Heating and Air in Central Point, we teach homeowners to separate that normal behavior from the real faults: a coil encased in ice, or a house that keeps getting colder.
Heat pumps are the fastest-growing heating equipment we install in Southern Oregon, and they work well here — but they behave differently from the gas furnaces most of our customers grew up with. This guide explains what's normal on a freezing night, what isn't, and when to call for heat pump and heating repair in the Rogue Valley. If you're still deciding between technologies, our comparison of heat pumps versus gas furnaces for Southern Oregon covers that question in depth.
What Is a Defrost Cycle, and Why Does It Blow Cool Air?
A defrost cycle is the heat pump briefly running in reverse — essentially air-conditioning mode — to melt frost off its outdoor coil. When your heat pump pulls heat out of cold, damp air, moisture freezes on the outdoor coil. Frost acts like a blanket that blocks heat transfer, so the system periodically reverses itself, sends hot refrigerant outdoors to melt the frost, and runs the indoor electric heat strips (if equipped) to temper the air inside.
During a defrost cycle you may notice:
• The indoor air turning cool or lukewarm for several minutes.
• A whooshing or swooshing sound as the reversing valve shifts — it can sound startling the first time.
• The outdoor fan stopping while the unit keeps humming.
On a foggy Rogue Valley morning with the kind of damp cold our valley inversions produce, defrost cycles happen more often. That is normal, not a defect.
Is Steam Rising Off My Heat Pump Normal?
Yes — steam billowing off the outdoor unit is one of the most misunderstood (and most normal) heat pump behaviors. During defrost, the coil heats up rapidly and the melting frost flashes into water vapor. It can look alarming, like the unit is smoking, and every winter we take calls from worried homeowners watching it happen. Steam that appears during a defrost cycle and clears within a few minutes means the system is working correctly.
When it's not normal: smoke that smells electrical or burnt is not steam — shut the system off at the thermostat and the breaker and call us. And if the unit never seems to clear its frost at all, keep reading.
What Are Auxiliary Heat and Emergency Heat?
Auxiliary heat is a backup heat source — usually electric resistance strips inside your air handler — that switches on automatically when the heat pump alone can't keep up or when the system is in defrost. Seeing "Aux Heat" on your thermostat during a cold snap is normal and requires no action from you.
Emergency heat ("Em Heat") is different: it's a manual setting that shuts the heat pump off entirely and runs only the electric strips. It exists for genuine failures — for example, if the outdoor unit is damaged or solidly iced and you need heat while you wait for a technician. Because resistance heat costs considerably more to run than the heat pump itself, don't use emergency heat as an everyday setting. If you find yourself relying on it just to stay warm, something is wrong and the system needs service.
How Warm Should the Air From a Heat Pump Feel?
Heat pump supply air is warm, not hot — noticeably milder than the blast a gas furnace produces. Because the air coming from the registers can be close to skin temperature, it can feel almost cool against your hand even while it is steadily heating the house. Heat pumps also run longer, gentler cycles by design, especially in cold weather; a heat pump running most of the evening during a freeze is normal operation, not a failing unit.
The test that matters is the room, not the register: if the house is holding the temperature you set, the system is doing its job. If the indoor temperature keeps sliding downward even with the system running continuously and aux heat engaged, that is a real symptom worth a service call.
Why Is My Heat Pump Iced Over — and When Is Ice a Problem?
A light coating of frost on the outdoor coil between defrost cycles is normal winter behavior. Solid ice is not. Call for service when you see:
• Ice encasing the coil, top, or fan that never melts off, even hours later.
• Thick ice returning quickly after every defrost.
• Ice caused by water dripping onto the unit — a leaking gutter above the heat pump is a surprisingly common culprit we find on service calls.
Persistent icing usually points to a failed defrost control, a bad reversing valve, low refrigerant charge, or an airflow problem — none of which are homeowner fixes. Safety caveats: never chip or pry ice off the coil (the fins and refrigerant tubing damage easily), and don't aim space heaters at the unit. If the unit is badly iced, switch the thermostat to emergency heat so the house stays warm without grinding the frozen outdoor unit, and call (541) 855-5521.
How Does Thermostat Staging Affect Heat Pump Performance?
Heat pumps reward steady setpoints and punish big swings. When you raise the setpoint several degrees at once — say, coming home to a house set way back — the thermostat sees a large gap and calls in the expensive auxiliary heat to close it quickly. Homeowners who grew up doing deep nighttime setbacks with a gas furnace often carry the habit over and then wonder why winter electric bills sting.
With a heat pump, keep setbacks modest — a couple of degrees — or use a heat-pump-aware smart thermostat that recovers gradually without triggering the strips. If you're an Oregon customer of Pacific Power or Portland General Electric, Energy Trust of Oregon currently offers a $100 smart thermostat incentive; amounts are reviewed annually, so confirm at energytrust.org.
What's Normal vs. a Real Fault in a Cold Snap?
Normal during freezing Rogue Valley weather: longer or near-continuous run times; milder supply air; periodic defrost cycles with steam and a whooshing sound; "Aux Heat" showing on the thermostat during recovery or deep cold; light frost between defrosts.
Real faults — call for service: indoor temperature falling steadily despite continuous running; the outdoor unit solidly iced or its fan not spinning; grinding, screeching, or metal-on-metal noises; the system relying on emergency heat to keep up; breakers tripping; or the outdoor unit not running at all. If the failure hits overnight during a freeze, our guide on what to do when your heating fails on a cold night covers protecting your home while you wait. And if your heat pump is well past its expected years and limping through every winter, compare its symptoms against the signs your HVAC is reaching end of life.
How Do You Keep a Heat Pump Reliable Through a Rogue Valley Winter?
Heat pumps run year-round — they don't get a summer or winter off — so maintenance matters more, not less. Keep the outdoor unit clear of leaves, snow drift, and stored items on all sides; keep gutters above it in good repair so meltwater doesn't drip and refreeze on the coil; and never cover the unit in winter (it needs to breathe, and covers trap moisture). Beyond that, professional maintenance catches weak capacitors, low charge, and defrost-control problems before the first freeze exposes them — our guide to how often you should service your HVAC system explains the cadence, and the Stone Comfort Membership Club (details here) handles the scheduling for you.
Frequently Asked Questions About Heat Pumps in Cold Weather
Should I switch my heat pump to emergency heat when it's freezing outside?
No — not unless the heat pump has actually failed. Emergency heat bypasses the heat pump entirely and runs electric resistance strips, which cost considerably more to operate. A properly working heat pump, with auxiliary heat engaging automatically as needed, will keep your home comfortable through Rogue Valley freezes without you touching that setting.
Why does my heat pump run constantly when it's cold?
Long, continuous run times in cold weather are normal heat pump behavior. As outdoor temperatures fall, there is less heat in the air to harvest, so the system runs longer and gentler cycles to keep up. Constant running only signals a problem if the indoor temperature is dropping at the same time.
Should I cover my heat pump in the winter?
No. A heat pump works all winter and needs unrestricted airflow across its outdoor coil to do it. Covers block that airflow, trap moisture against the cabinet, and give rodents a sheltered home. Just keep the unit clear of leaves, snow, and debris on all sides.
Why did my electric bill jump during the last cold snap?
Almost always because auxiliary electric heat ran more than usual. Deep thermostat setbacks, an undersized or aging heat pump, or a defrost problem can all push the system onto its resistance strips for long stretches. If aux heat seems to run constantly even in moderate cold, have the system checked.
Do heat pumps stop working below freezing?
No — modern heat pumps, especially cold-climate models, continue producing heat well below freezing, and typical Rogue Valley winter lows are well within their working range. Output does decline as temperatures fall, which is exactly why systems include auxiliary heat to bridge the coldest nights.
The Bottom Line for Cold-Weather Heat Pump Worries
Steam, whooshing sounds, mild supply air, and long run times are a heat pump speaking its native language — not crying for help. A solidly iced unit, a cooling house, or a thermostat stuck on emergency heat are the real red flags, and those are worth a call to Stone Heating and Air at (541) 855-5521 — NATE-certified technicians, 4.9-star rated, on call 24/7 across the Rogue Valley. And if this winter has you questioning whether a heat pump is even the right fit for your home, our side-by-side guide to heat pumps versus gas furnaces in Southern Oregon gives you the honest comparison before you spend a dollar.