The forecast drops: what a polar vortex really means for your heat pump
When the weather app warns of a polar vortex, we’re talking about outdoor air plummeting well below 0°F, sometimes to –20°F or –30°F with harsh wind chills. Heat pumps can still work, but everything gets harder: the unit must squeeze tiny bits of heat out of very cold air, run longer, and rely on backup stages more often. Our goal here is simple: keep heat moving, prevent ice from winning, and avoid costly emergencies. We’ll walk through quick checks you can do safely, when to call a pro, and how to prep for the next cold snap.
Think of this as your neighbor-tech guiding you step-by-step. If you need gear or want a second opinion, Our Help Center we’re happy to help you sort it out before it becomes a no-heat call.
How heat pumps behave in extreme cold (and why “balance point” matters)
Heat pumps are most efficient above freezing. Around 32–38°F (the balance point), the system needs help from auxiliary heat to keep up. Many newer units are rated down to –13°F, but output still drops as the temperature falls. That’s normal physics, not a defect. During a polar vortex, expect:
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Longer run times to maintain temperature.
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More frequent defrost cycles to clear coil frost.
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Short swings in indoor temperature, even when everything’s working.
Your job is to reduce obstacles: keep airflow clear, control sensible, and ice in check. If your home is drafty, the heat pump must fight both the cold and infiltration air sealing and insulation are quiet heroes here. If you’re planning upgrades, our Design Center can help size and match equipment, and our Sizing Guide explains the basics so you know what “right-sized” looks like in cold climates.
Five-minute triage: easy, safe checks before you worry
Before diving deep, take five minutes:
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Thermostat: Set to HEAT and HOLD; avoid big jumps. If you’re struggling, try raising 2–4°F above normal to get ahead.
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Power: Confirm the outdoor disconnect is in, and breakers for both indoor and outdoor units are on. Reset a tripped breaker once only.
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Airflow: Open supply vents and clear return grilles.
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Filters: If you haven’t checked in a while, replace now (see next section).
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Snow & ice: Make sure the outdoor unit can breathe (we’ll cover how).
If the system won’t start, trips again immediately, or makes grinding/screeching sounds, stop and call a pro. Snap a quick photo of the setup and breakers—if you need us to take a look, you can use Quote by Photo for fast guidance.
Airflow basics: filters and vents that won’t choke your heat
When it’s dangerously cold, dirty filters are the silent system killer. Restricted airflow means lower heat output, longer run times, and sometimes coil icing. During a polar vortex, check filters weekly (not monthly). Replace if there’s any question—filters are cheap insurance. Also:
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Open every supply vent at least 80–100%. Closing rooms can raise static pressure and reduce overall delivery.
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Clear returns of furniture, drapes, pet beds.
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If you use thicker media filters, keep a spare on hand so you’re not stuck during a storm.
If your air handler or coil is older, upgrading can improve airflow, defrost performance, and comfort. Browse Air Handlers; small improvements here prevent big headaches when the mercury tanks.
Outdoor unit care: snow, clearance, and the “don’t smother it” rule
Your outdoor unit needs room to breathe and a path to drain meltwater during defrost. Follow these cold-weather musts:
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Keep 2–3 feet of clearance on all sides and above.
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Brush off snow on top—don’t let a cap of snow trap defrost steam into ice.
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Shovel paths so air can flow through the coil and water can drain away.
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Avoid leaning plywood or tarps against the cabinet; it traps moisture and ice.
If drifting is severe, a simple wind break a few feet away (not touching the unit) can help. Elevated stands are great in heavy-snow regions. If you need line repairs or extensions when moving a unit, see our Line Sets.
Frost vs. “ice box”: understanding defrost cycles (and when they’re not normal)
A thin, even frost on the coil is normal. Your heat pump periodically switches into defrost (it briefly runs like AC) to warm the outdoor coil and melt frost. Typical defrost:
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Every 30–90 minutes, for 5–15 minutes.
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Steam rises; you may hear a swoosh as the reversing valve shifts.
Ice that encases the whole unit, frost that never clears, or defrosts that run too often or too long. Quick checks:
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Make sure sensors are attached to the coil where they belong.
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Confirm the fan spins freely after defrost.
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Watch defrost intervals; note times/temps in your log.
If ice persists beyond 30 minutes or returns immediately, stop and call a pro—continued operation can damage the compressor. For stubborn icing or replacement planning, our R-32 Heat Pump Systems include cold-climate options that manage frost more effectively.
When auxiliary heat won’t quit: setpoints, staging, and sizing
Auxiliary (electric heat strips or other backup) should assist below the balance point or during defrost, not run constantly above ~35°F. If it does:
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Thermostat tactics: Use a heat-pump-compatible, multi-stage thermostat. Avoid rapid bumps that call for AUX. Make 1–2°F changes and wait.
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Hold steady: During a cold snap, use HOLD instead of deep setbacks.
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Sizing reality: An undersized heat pump leans on AUX too much in cold weather. If your home never hits setpoint without AUX, sizing or envelope upgrades may be needed.
Still battling the AUX light? Consider a dual-fuel path pair a heat pump with a gas furnace for extreme lows. Browse R-32 Residential Dual-Fuel Packaged Units or ask our Design Center for a balance-point review.
Refrigerant red flags: what you can spot (and what to leave to pros)
Low refrigerant can cause long run times, weak heat, and ice on refrigerant lines. You might hear a hissing sound, or performance may be poor in both heating and cooling seasons. Here’s how to proceed safely:
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Look, don’t open: If you see ice on the copper lines or the coil, note it and power off the system to prevent damage.
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Don’t add refrigerant yourself EPA rules apply, and mischarging hurts compressors.
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Capture clues: Photos of iced lines, gauge readings (if available on a smart stat), and your temperature log speed up diagnosis.
If a leak is confirmed, discuss repair vs. upgrade. In cold regions, modern R-32 split systems and Ductless Mini-Splits can deliver better low-temp performance and zoning benefits.
Reversing valve & compressor stress: the sounds you shouldn’t ignore
Two key components work extra hard in a vortex:
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Reversing valve: Lets the system switch between heating and defrost. Warning signs: stuck in one mode, harsh clack without switching, or no heat returning after defrost.
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Compressor: Can strain, overheat, or short-cycle in extreme cold. Warning signs: grinding, rattling, screeching, failure to start, or frequent breaker trips.
Your “during the storm” playbook: run smart, stay warm
When temps nosedive:
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Monitor: Glance outside every few hours for ice buildup and clear snow gently.
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Doors: Keep garage and exterior doors closed; limit openings to trap heat.
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Fan mode: Use continuous fan only if you have a high-efficiency variable-speed motor (ECM). Otherwise, leave on AUTO to avoid cooling the ductwork.
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Humidity helps comfort: Boil water, soup on the stove, or run a humidifier—moist air feels warmer.
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Expect minor drops: At –20°F to –30°F, even a healthy system may struggle to hold your exact setpoint. That’s normal under design limits.
If you need backup room heating, ensure it’s listed and safe. And if tonight exposes system gaps, start planning upgrades with our Ductless Mini-Split Options and Package Units once the weather breaks.
Win the next vortex: a simple pre-winter checklist
A little prep in fall saves panic in January. Put these on your calendar:
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Pro tune-up: Verify refrigerant, defrost operation, electrical connections, and coil cleanliness.
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Filter plan: Stock two spare filters; change before first deep freeze.
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Thermostat check: Calibrate, confirm heat-pump mode, and test staging.
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Outdoor unit reset: Level the pad, clear shrubs to 2–3 feet, consider a stand if snowdrifts are common.
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Home envelope: Seal obvious leaks; add insulation where it’s thin.
If you want a pro layout, our Design Center can match equipment to your home, and HVAC Financing can spread costs comfortably.
