Updated October 27, 2026
Thin white frost on a heat pump on a cold, damp Northern Virginia morning is normal, and the defrost cycle melts it off in a few minutes. A heat pump frozen into a solid block, iced over on top, or still white hours later is not, and that one is a call. If the frost is light, try the checks below first. If the ice is thick or the fan has stopped, call (703) 997-9757 or book heat pump repair, where the diagnostic visit is $99.
Carrier draws the line at a quarter inch: a thin layer of frost under that is normal winter operation, and a thick coat or solid ice is not. Below is how to tell which one you have, why heat pumps steam and run nonstop in the cold, the five kinds of ice that mean something is wrong, what you can safely do yourself, and what the fix costs.
Heat pump frozen or just frosted? How to tell in ten seconds
Walk outside and look at the coil, the thin metal fins that wrap the sides of the outdoor unit. Then answer three questions.
- Can you still see the fins? A white dusting, like frost on a windshield, with the fin pattern showing through, is normal. A smooth glaze of ice with no fins showing is not.
- Is the fan turning? The big fan on top should spin whenever the unit runs. It stops on purpose for a few minutes during defrost. If it sits still for a long stretch while the unit hums, or ice has grown up into the blades, that’s a problem.
- Does it come and go? Normal frost builds, melts in a defrost cycle, and builds again. Ice that stays all afternoon, or gets thicker every hour, is the unit telling you defrost isn’t working.
Fins showing, fan turning, frost that comes and goes: leave it alone. That’s a heat pump doing its job in the weather we get here from December through February. Raw, damp mornings just above freezing are the frostiest, which is why your unit and your neighbor’s both look white at 7 a.m. and clean by lunch.
Any other answer, keep reading. The next sections cover what the steam means, the five kinds of ice that aren’t normal, and what you can do about each one before anyone comes out.
Heat pump steaming? That’s defrost mode doing its job
A cloud of steam rolling off the outdoor unit looks alarming, and it’s almost always fine. It’s the defrost cycle. When frost builds on the outdoor coil, the heat pump reverses itself for a few minutes and sends warm refrigerant through that coil so the frost melts. Trane describes the steam as the ice melting and evaporating, and lists what else you’ll notice: the outdoor fan stops, there’s a whoosh as the valve shifts, and the compressor sound rises or falls.
How long it lasts depends on the brand. Trane says a cycle usually runs 3 to 5 minutes. Carrier says 5 to 10. Lennox says 5 to 15, and that the unit checks for frost every 30 to 90 minutes. Lennox also explains the pattern you’ll notice over a week: on cold, damp days it defrosts often, and on dry, sunny days it may barely defrost at all.
The house still needs heat while the outdoor coil is busy melting frost, so the backup heat in the indoor unit comes on. In most homes that’s electric heat strips. That’s why the thermostat may show Aux Heat during defrost. Our post on aux heat versus emergency heat covers what each thermostat setting does and when that Aux light means something is wrong.
So when is defrost the problem? Trane’s answer is the one to remember: if the heat pump seems to switch into defrost constantly, or each cycle lasts longer than the one before, have it looked at. Steam for a few minutes every hour or so on a raw morning is normal. Steam that never stops, or a unit that’s iced up between defrosts, is not.
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Five kinds of heat pump ice and what causes each one
When the ice isn’t normal, where it sits tells you a lot about why. Lennox’s frozen heat pump guide lists the usual causes, and they line up with what the ice looks like.
1. A solid block, coil and all
The whole unit is glazed over and the fins are gone. That usually means defrost never ran. Lennox points to a failed defrost control board, timer or sensor. The defrost board is the part that tells a heat pump when to melt the frost off its coil, and when it quits, the coil turns into a block of ice. Replacing a defrost board runs $450 to $1,150. Sometimes it’s only the sensor that tells the board the coil is warm when it isn’t, and a technician tests that before anything gets replaced.
2. Ice on top, from a gutter or roof drip
A thick cap on top of the unit, icicles hanging off the fan grille, and sides that look fairly clean. That’s water landing on the unit from above and freezing as it lands: a gutter that overflows, a downspout that empties beside it, a roof edge that drips. Defrost can’t keep up with water poured on it all day. Lennox’s fix is to keep gutters and downspouts from draining onto the unit. This is the kind you can often solve yourself, with a gutter cleaning or a downspout extension, once you know nothing underneath got damaged.
3. Ice from the bottom up
Ice building from the base, sometimes climbing into the bottom of the coil. The melt water from defrost has nowhere to go. The pad has sunk so the unit sits in a puddle, snow is packed around the base, or the drain openings are blocked, so the water pools and refreezes. Lennox lists a clogged drain pan or line among the causes. Getting the unit level and clear underneath is the fix.
4. Patchy ice, or ice on the refrigerant lines
Frost on only part of the coil, or ice on the copper lines that run into the house. That pattern points to low refrigerant, which Lennox lists as a cause, and low refrigerant means a leak somewhere. Adding refrigerant without finding the leak only puts off the next freeze. This one needs a technician with gauges.
5. Ice with the fan stopped
The fan on top isn’t turning, outside a short defrost pause, and ice is building fast. A failed outdoor fan motor is on Lennox’s list. Before the motor itself, a technician checks the run capacitor, the part that gives the motor its push to start. A weak one is the motor that hums and never gets going, and replacing it runs $240 to $370.
One more cause sits indoors: restricted airflow. Lennox notes a clogged filter can add to icing. That’s why the filter is on the checklist of things you can do yourself, a few sections down.
Heat pump running constantly in cold weather: normal or not?
Mostly normal, as long as the house holds temperature. Carrier’s troubleshooting guide says it can be completely normal for a unit to run all the time in extreme temperatures. A heat pump pulls heat out of the outdoor air, and the colder the air, the less heat there is to pull, so on a 20 degree night it may run for hours without a break to keep the house at 68. Long run times on the coldest nights aren’t a defect. They’re how a heat pump works.
What isn’t normal:
- The house won’t hold the set temperature on a mild day in the 40s.
- The outdoor unit is silent while the indoor unit runs and the Aux Heat light stays on. The contactor, the relay that powers the outdoor unit, may be stuck, and the backup heat is doing all the work. A contactor runs $290 to $425.
- It runs nonstop and it’s iced up. A frozen coil moves almost no heat, so the unit runs and runs and the backup heat carries the house.
- Air from the vents feels cool for long stretches outside defrost.
The backup heat in most heat pump homes is a set of electric heat strips inside the indoor unit. They work, and they’re what keeps the house warm when the outdoor unit can’t keep up. The short below shows one of our technicians fitting a heat strip kit inside an air handler, so you can see what’s in there.
For how heat pumps handle the coldest stretch of the year here, read heat pumps in a Virginia winter. If your backup is a gas furnace instead of heat strips, dual fuel heat pumps explains how the switch between the two works.
What you can safely do about a frozen heat pump
Start with the easy checks. None of them take tools or a panel off.
- Clear the snow. Shovel it back from the sides so air can reach the coil, and don’t pile it against the unit. Brush light snow off the top with a broom, never a shovel edge or anything sharp. Both are Lennox’s advice.
- Check the filter. A clogged filter chokes airflow through the indoor unit. ENERGY STAR says to inspect it monthly on a heat pump system. If it’s gray and matted, change it.
- Find the drip. If the ice is on top, look up: gutter overflow, a downspout aimed at the unit, a drip line off the roof. Redirecting the water is the fix, and you can do it on a dry day.
- Check the thermostat. It should be on Heat, not Cool, with the fan on Auto. Carrier lists the thermostat mode as a first check.
If the ice is thick, a solid coat or more than a quarter inch, Carrier’s advice is to turn the system off and call. That keeps the outdoor unit from grinding away with a frozen coil. To keep the house warm while it thaws, set the thermostat to Emergency Heat, which shuts the outdoor unit off and runs the backup heat on its own, the way our aux heat post explains it. Then give it time. Lennox says to call a technician if the ice doesn’t melt in 6 to 8 hours or comes right back.
What not to do
- Don’t chip or pry the ice. Lennox is direct about this: tools damage the coil, the fins and the fan blades. A punctured coil turns a frozen unit into a refrigerant leak.
- Don’t pour hot water on it. Lennox says never. The water refreezes on the coil and the base, and you’ve added ice.
- Don’t open the panels. There’s high voltage inside, and the defrost board and capacitor are not homeowner parts.
- Don’t leave it on Emergency Heat for weeks. Emergency Heat is a stopgap. Whatever froze the unit is still there, and the heat strips are carrying the whole house alone.
When to call about a frozen heat pump, and what it costs
Call if any of these are true:
- The coil is under solid ice, or a coat thicker than a quarter inch (Carrier).
- The ice hasn’t melted after 6 to 8 hours off, or it refreezes soon after it thaws (Lennox).
- The fan doesn’t spin once the ice is gone (Lennox).
- Defrost runs constantly, or every cycle runs longer than the last (Trane).
- There’s ice on the copper refrigerant lines.
- The outdoor unit is silent while the indoor unit runs on backup heat.
Here’s what the usual parts behind a frozen heat pump cost in Northern Virginia, the same rows our heat pump repair page prints. Every repair starts with the $99 diagnostic visit, and you get the price in writing before any work starts.
| Repair | What it is | Range in Northern Virginia |
|---|---|---|
| Diagnostic visit | A technician finds why it froze before anything gets replaced. | $99 |
| Run capacitor replaced | Gives the fan and compressor motors their push to start. A weak one hums and never gets going. | $240 to $370 |
| Contactor replaced | The relay that powers the outdoor unit. Stuck, it leaves the backup heat doing all the work. | $290 to $425 |
| Thermostat replaced | Wired and set up for a heat pump, backup heat settings included. | $300 to $640 |
| Defrost board replaced | Tells the heat pump when to melt the frost off its coil. When it fails, the coil turns into a block of ice. | $450 to $1,150 |
| Control board replaced | The brain of the air handler. When it goes, the parts downstream stop doing what they’re told. | $550 to $1,180 |
| Blower motor replaced | The indoor fan motor. The spread is a standard motor against a variable speed one. | $670 to $2,400 |
The six common repairs run $240 to $2,400. A refrigerant leak is its own job: finding the leak, fixing it and recharging the system gets priced once the technician knows where it’s leaking, so it isn’t in the table. For every price and what moves each one, read heat pump repair cost in Northern Virginia.
On Comfort+, the diagnostic visit is included, and half of each repair bill is banked toward replacing that system, up to $1,500. The plan is $199 a year.
Before the first hard freeze: a fall check on the heat pump
ENERGY STAR’s maintenance checklist puts a contractor check-up on the heating system every fall, before the season starts. For a heat pump, that’s the visit where someone tests the parts that tend to give out in the cold while the weather is still mild.
That’s what our $67 Heating Check is for, on one furnace or heat pump, through December 31. The technician tests the electrical components, checks the thermostat and sets it up properly, measures airflow and temperature rise, and takes photos of anything we flag, so you see what we saw. It can’t stop a gutter from dripping on the unit in a January storm. It does catch a weak part on a mild afternoon instead of a frozen night. Every deal running this fall is on the offers page.
Heat pump repair in your part of Northern Virginia
We fix frozen and iced heat pumps across Northern Virginia, from Loudoun down to Prince William. Find your town: Chantilly, Herndon, Reston, McLean, Burke, Springfield, Sterling, Leesburg, Woodbridge, and Arlington. Don’t see yours? The full list is on our service areas page.
Frozen heat pump questions
Why is my heat pump covered in ice?
A thin layer of frost is normal in cold, damp weather and melts off in a defrost cycle. A heat pump covered in ice, with the fins hidden, usually means defrost isn’t running (a defrost board, timer or sensor), water is dripping on it from a gutter or roof, refrigerant is low from a leak, airflow is blocked, or the outdoor fan has stopped. If the coat is thicker than a quarter inch or won’t clear, turn it off and call.
Is it normal for a heat pump to steam in winter?
Yes. The steam is frost melting off the outdoor coil during a defrost cycle. The fan stops, you may hear a whoosh, and it lasts a few minutes: Trane says 3 to 5, Carrier 5 to 10, Lennox 5 to 15. Steam that never stops, or defrost cycles that keep getting longer, is worth a call.
How long does a heat pump defrost cycle last, and how often does it run?
A few minutes, somewhere from 3 to 15 depending on the brand. Lennox says the unit checks for frost every 30 to 90 minutes, defrosts more often on damp days, and barely at all on dry, sunny ones.
Why is my heat pump running constantly in cold weather?
On the coldest nights it’s normal. Carrier says running all the time in extreme temperatures can be completely normal, because there’s less heat in the outdoor air to pull. It’s a problem when the house won’t hold temperature on a mild day, the outdoor unit is silent while the backup heat runs, or it’s running with an iced coil.
Can I pour hot water on a frozen heat pump?
No. Lennox says never. The water refreezes on the coil and the base, and you’ve added ice. Turn the system off, set the thermostat to Emergency Heat to keep the house warm, and let it thaw.
Should I chip the ice off my heat pump?
No. Tools bend the fins and can puncture the coil or damage the fan blades, which Lennox warns about, and a punctured coil is a refrigerant leak. Clear snow from around the unit with a broom and let the ice melt on its own or call.
Should I turn off a frozen heat pump?
If it’s a solid coat or thicker than a quarter inch, yes. Carrier says to turn the system off and call. Use Emergency Heat to keep the house warm in the meantime. If the ice hasn’t cleared in 6 to 8 hours or it refreezes, Lennox says to call a technician.
How much does it cost to fix a frozen heat pump in Northern Virginia?
The diagnostic visit is $99. The usual repairs behind a frozen unit run $240 to $2,400: a run capacitor $240 to $370, a contactor $290 to $425, a defrost board $450 to $1,150. A refrigerant leak is priced once the technician finds where it’s leaking.
Will a frozen heat pump thaw on its own?
Normal frost does, every defrost cycle. A heat pump that’s frozen solid may thaw on a warm afternoon and freeze again overnight, because whatever stopped the defrost is still there. Lennox says to call if it refreezes quickly.
Ice that won’t clear? Here’s how to reach us
If you’ve cleared the snow, checked the filter and fixed the drip, and the ice is still there, it’s time for a technician. Call (703) 997-9757 day or night, use the form at the top of this page, book online, or read more about our heat pump repair service. Bring the details you noticed: where the ice sits, whether the fan turns, and what the thermostat says. They help the technician start in the right place.
SwiftPro Heating, Cooling & Plumbing services, repairs and installs furnaces, heat pumps, air conditioners, ductless mini splits and hot water boilers across Northern Virginia from Chantilly and Ashburn, with a dedicated HVAC team and a separate plumbing team. Family owned, BBB Accredited with an A rating, 24/7 emergency service, Virginia Class A contractor license 2705192276, and rated 5.0 stars across 1,130 reviews on Google, Angi, Yelp, the BBB and Facebook. Read the reviews.
