Heat pump winter: what's normal
Annual · typically December
Why it matters
Heat pumps do things in winter that LOOK broken to anyone raised on furnaces, and with ~60–120 freeze days a year in your county, yours will do all of them. The service companies know this — the first cold snap fills their books with "emergency" calls that end with a tech watching a defrost cycle finish and writing an invoice. Five minutes of knowing-what's-normal is worth real money here.
Normal: A frost ring or light frost coat on the outdoor coil. Every 30–90 minutes, the unit pausing, whooshing, and blowing a dramatic cloud of steam for a few minutes — that's defrost, melting the frost off the coil, and the steam is the proof it's working. Slightly cool-feeling air from vents (heat pump air is ~90–100°F — warmer than the room, cooler than your hand). The "aux" or "em heat" indicator flickering on during recovery from a setback or in a hard snap.
Not normal: The outdoor unit encased in solid ice — an ice block, not frost — especially with a gutter dripping onto it from above. Aux heat running constantly in mild (40°F+) weather. Defrost steam every 10 minutes. Ice sheets ON the fan blades. Those earn a call.
What skipping it costs
$90–$400
This card's math runs backwards: the cost isn't neglecting the machine, it's not knowing what's normal. Steam clouds, whooshes, frost rings, the aux-heat light — every one of them generates panicked $150–$400 winter service calls for units that are doing exactly their job.
Two ways to get it done
Do it yourself
- In December, walk out and look at the unit during a cold stretch. Frost coat: fine. Ice block: fix the water source above it (usually a gutter or roof drip line) and call if it doesn't clear.
- Make sure defrost meltwater can drain — a unit on risers or gravel doesn't refreeze its own puddle.
- Never chip ice off the coil with anything hard. Warm water from a watering can, or just let defrost do its job.
- Inside: know where the "emergency heat" switch is, and leave it OFF unless the heat pump is actually dead. Em heat is pure electric-strip heating at 2–3× the cost — it's the limp-home mode, not a comfort setting.
Hire it out
$90–$180National fair range — local labor moves this number.
A legitimate winter diagnostic runs $90–$180 and should end with measurements: defrost board behavior, sensor readings, aux staging. What it shouldn't end with is a refrigerant top-off "to get you through the winter" — if a leak is suspected, the honest move is a leak search, usually scheduled for milder weather when charging can be done right.
And if the unit truly is struggling in the cold, insist the conversation start with the small stuff — defrost sensor, board, reversing valve — before anyone says the word "replacement" in the middle of the coldest, highest-priced week of the year.
Ask the tech
- Was that a normal defrost cycle, or is the defrost control actually failing? What did you measure?
- How often is aux heat running, and is that reasonable for these temperatures?
Red flags you're being upsold
- A winter refrigerant 'top-off.' Charging a heat pump accurately in cold weather is genuinely difficult, refrigerant doesn't get consumed, and the January top-off is the oldest play in the book.
- 'Heat pumps don't work in the cold, you should add/replace with a furnace' — modern units heat efficiently well below freezing; a tech leading with that pitch is selling equipment, not fixing yours.
- An emergency-rate visit for steam coming off the unit. That's a defrost cycle. It's Tuesday.
Second opinion time: Any December diagnosis that ends in 'replace the system' — cold-snap replacement pricing is the worst pricing there is.
The call
DIY — this one's just knowledge. Read it in December, and you'll skip the most common unnecessary service call in cold-climate HVAC.