Ice forms on your dehumidifier when the air is too cold or too dry for the unit to work safely
A dehumidifier that ices up is running into a physical problem, not a malfunction. When air temperature drops below about 65°F, or when humidity is already very low, moisture condenses on the cold evaporator coil inside your unit faster than it can drain away. That moisture freezes solid, blocking airflow and stopping the dehumidifier from working. The ice buildup also risks damaging the compressor if you keep running it.
The good news: this is preventable, and the fix depends on what caused it. Most of the time, you either need to move the dehumidifier to a warmer room, raise the humidity setting, or both.
Key Takeaways
- Dehumidifiers ice up when the air temperature falls below 65°F or the humidity level is already very low, because moisture freezes on the cold coil inside.
- Running a dehumidifier in a cold basement, garage, or unheated space is the most common cause of icing.
- Most modern dehumidifiers have an automatic shutoff that stops the unit when it senses frost, but older models may not.
- The fastest fix is to move the unit to a warmer room or raise the humidity setting on the dial so the coil does not get as cold.
- If ice has already formed, unplug the unit and let it thaw at room temperature before restarting it.
Cold air is the main reason dehumidifiers freeze
Dehumidifiers work by pulling warm, humid air across a cold evaporator coil. The moisture in the air condenses on that coil the same way water beads up on a cold window. Normally, that water drains into a tank or hose. But when the air temperature drops, the coil gets colder than the dew point of the air around it, and the condensed water freezes before it can drain.
This happens most often in basements, crawl spaces, garages, and other unheated rooms where the temperature stays below 65°F. It also happens in heated spaces during winter if the dehumidifier is placed near an outside wall, a cold window, or an air conditioning vent. Even a few degrees of temperature difference can trigger icing.
If you are running a dehumidifier in a space that is naturally cold, moving it to a warmer room is usually the simplest solution. If that is not possible, look for a dehumidifier model rated for low-temperature operation—some are designed to work down to 41°F or lower.
Low humidity levels can also cause ice to form
A dehumidifier can ice up even in a warm room if the humidity is already very low. This happens because the unit keeps running and pulling moisture out of the air, making it drier and drier. As the air dries out, the evaporator coil gets colder relative to the air around it, and frost forms.
Most dehumidifiers have a humidity dial or digital setting that tells the unit to stop running once the air reaches a certain moisture level—usually between 30 and 60 percent relative humidity. If your dial is set too low, or if you have it set to continuous mode, the unit will not shut off and will keep trying to remove moisture that is no longer there.
The fix is straightforward: raise the humidity setting on your dehumidifier to 50 or 60 percent. This tells the unit to stop running once the air is dry enough for comfort, preventing the coil from getting too cold. You can also switch the unit to a timer mode if it has one, so it runs for set periods rather than continuously.
Automatic frost sensors may not work on older units
Many modern dehumidifiers have a built-in frost sensor that detects when ice is forming on the coil and automatically shuts the unit off. This is a safety feature that prevents damage to the compressor and stops ice from building up. If your dehumidifier has this feature, it should stop on its own when conditions are too cold or too dry.
Older dehumidifiers, or very inexpensive models, may not have a frost sensor. If you own one of these units, you need to monitor it yourself and turn it off if you notice ice forming. Running an unprotected dehumidifier in freezing conditions can damage the compressor and shorten the unit's life.
Check your owner's manual to see whether your model has a frost sensor. If it does not, avoid using the dehumidifier in spaces below 65°F or with humidity settings below 40 percent.
How to thaw a frozen dehumidifier safely
If ice has already built up on your dehumidifier, unplug it when ready and leave it unplugged. Do not try to chip away the ice or pour warm water on it—you risk damaging the coil or creating an electrical hazard.
Move the unit to a warm room (above 70°F if possible) and let it sit for several hours. The ice will melt on its own as the coil warms up. Once the unit is completely thawed and dry inside, you can plug it back in and restart it. Before you do, make sure you have fixed the underlying problem—either by moving it to a warmer space or by raising the humidity setting.
If water leaks out while the unit is thawing, place it on a towel or in a shallow pan to catch the drainage. This is normal and not a sign of damage.
When to call a professional
If your dehumidifier continues to ice up after you have moved it to a warmer room and raised the humidity setting, the frost sensor may be faulty or the unit may have a refrigerant leak. These are internal problems that require professional repair. A technician can test the sensor, check the refrigerant level, and determine whether the unit is worth fixing or should be replaced.
If the dehumidifier has been frozen for a long time and you hear unusual noises when you restart it, the compressor may have been damaged. Stop using it and have it inspected before running it again. Continuing to run a damaged compressor can cause it to fail completely and make the repair much more expensive.
Preventing ice from forming in the first place
The best approach is prevention. If you need to use a dehumidifier in a cold space, choose a model with a low-temperature rating and a frost sensor. Keep the humidity setting between 40 and 60 percent, and check the unit regularly during the first few days of use to make sure it is not icing up.
In basements and other naturally cold spaces, consider running the dehumidifier only during warmer months, or use it in combination with a space heater to keep the air temperature above 65°F. This is more energy-efficient than running a dehumidifier in a cold environment where it will struggle to work.
If you are using a dehumidifier to dry out a space after water damage, make sure the room temperature stays above 65°F. If it does not, the dehumidifier will ice up and stop working just when you need it most.
Frequently Asked Questions
Can I use a dehumidifier in an unheated basement?
Not safely with a standard dehumidifier. Basements stay cold year-round, and most units will ice up below 65°F. If you need to dehumidify a cold basement, look for a model rated for low-temperature operation, keep it set to 50 percent humidity or higher, and make sure it has a frost sensor. Alternatively, run a small space heater in the basement to keep the air warm enough for the dehumidifier to work.
What humidity level should I set my dehumidifier to?
Between 40 and 60 percent relative humidity is comfortable for most homes and prevents icing. If you are in a cold space, keep it at 50 percent or higher. If you notice frost forming, raise the setting when ready. You can lower it again once you move the unit to a warmer room.
Will my dehumidifier automatically turn off if it ices up?
Only if it has a frost sensor, which most modern units do. Check your manual to be sure. If your dehumidifier does not have one, you need to monitor it yourself and turn it off if you see ice forming. Running an unprotected unit in freezing conditions can damage the compressor.
Is it safe to leave a dehumidifier running overnight?
Yes, as long as the room temperature stays above 65°F and the humidity setting is not too low. If you are concerned about icing, use a timer to run the unit for a few hours at a time rather than continuously, or move it to a warmer room.
Can I use a hair dryer to melt ice off my dehumidifier?
No. Using a hair dryer or any heat source risks damaging the coil and creating an electrical hazard. Unplug the unit and let it thaw naturally in a warm room. This takes a few hours but is safe and will not damage the dehumidifier.