Heat Pump Frozen
A thin layer of frost on a heat pump in winter is normal; the unit melts it in a defrost cycle every 30 to 90 minutes. A thick block of ice that stays for hours means something is wrong, often a failed defrost control or sensor, low refrigerant, a stopped outdoor fan or blocked airflow. Typical repairs cost $150 to $650; refrigerant leak repair can reach $1,600.
Typical pro cost
$150 to $1,600
- Urgency
- Fix today
- DIY difficulty
- Medium
- Time to fix
- 1 to 3 hours (pro)
- Prices
- US typical range
Last reviewed October 2026
Signs it's this problem
- The whole outdoor coil is covered in thick ice
- Ice stays on the unit for hours
- Steam never appears from the unit (no defrost cycle)
- The house feels cooler and the backup heat runs a lot
- Ice builds up on the top or the fan blades
Common causes
Failed defrost control board or sensor
If the unit never switches into defrost, ice keeps building on the coil.
Low refrigerant
A leak makes the coil run colder and ice up more than normal.
Outdoor fan not running
Without airflow over the coil, frost turns into thick ice.
Blocked airflow
Snow, leaves or a dirty coil stop air from moving through the unit.
Dripping gutters
Water falling onto the unit freezes on top and over the fan.
How to fix it, step by step
- 1
Make sure the unit is not just in a normal defrost cycle: it may stop the fan and give off steam for a few minutes.
- 2
Clear snow, ice and leaves from around and on top of the unit with your hands or a soft brush.
- 3
Check that the outdoor fan runs when the unit is heating. If it hums but does not spin, turn off power and call a technician.
- 4
To melt ice, switch the thermostat to emergency heat or off, then pour lukewarm (not boiling) water over the coil.
- 5
Fix dripping gutters above the unit, and raise the unit on a stand if snow buries it.
- 6
If thick ice comes back within a day, book a technician to test the defrost control and refrigerant.
Tools and materials
- Soft brush
- Bucket of lukewarm water
- Flashlight
Approximate DIY cost: $0
Call a pro when
- Thick ice returns within a day
- The outdoor fan is not spinning
- You hear hissing or see oily spots on the lines
- The house cannot keep warm
Heat Pump Frozen cost
| Job | Typical cost |
|---|---|
| Typical heat pump repair | $150–$650 |
| Defrost control board replacement | $200–$600 |
| Defrost sensor or thermostat replacement | $150–$350 |
| Leak repair and recharge | $200–$1,600 |
| Outdoor fan motor replacement | $300–$700 |
Ranges are typical US prices compiled by FixHomeCost. Prices vary by region, home and contractor, so compare 2–3 local quotes.
Common questions
Is it normal for a heat pump to have ice on it?
Light frost is normal in cold, damp weather. The unit should melt it in a defrost cycle. A solid block of ice is not normal.
How often should a heat pump defrost?
Usually every 30 to 90 minutes in frosty conditions, for about 5 to 15 minutes each time.
Can I pour hot water on a frozen heat pump?
Use lukewarm water and pour gently with the unit off. Boiling water and tools can damage the coil.
Will a frozen heat pump damage the compressor?
It can if left running iced up for a long time, because refrigerant may return to the compressor as liquid. Get it checked if the ice keeps coming back.
Related guides
This is general information, not a professional inspection. See how we research costs.