Last Updated on September 1, 2026 by Umar Farooq
Most homes don’t need a dehumidifier in winter, and a lot of the ones that do are running a machine too cold to work. Cold outdoor air holds very little water, and your heating dries the house further, so indoor humidity usually falls on its own from about November. The exceptions are real, though — basements, crawl spaces, unheated rooms and anywhere you dry laundry indoors.
There are actually two questions tangled together here, and they have different answers. Let me separate them, because doing that resolves most of the confusion.
Question one: will it even work?
This is the mechanical question, and it’s answered by the room temperature rather than the calendar.
A compressor dehumidifier makes a coil cold and condenses water onto it. In a cold room the coil drops below freezing and frost forms instead of water. Below about 18°C / 65°F output falls away sharply. Below 5°C / 41°F, frost forms faster than the machine can clear it — GE’s own documentation puts the practical limit right there.
When that happens, the unit cuts the compressor and keeps the fan running to melt the ice off. From where you’re standing that looks like a broken machine blowing air around for no reason. It isn’t. That’s the defrost cycle working exactly as designed, and it’s the single most common winter complaint I see — I’ve written up the full symptom in why the fan runs but the compressor doesn’t.
So: in a heated room at 19°C, your machine is fine all winter. In an unheated garage at 4°C, it is not going to collect much no matter what you do to it.
Question two: should you be running one at all?
This one is answered by your hygrometer, not by the season.
Put a meter in the room for a week. Then:
| Reading | What to do |
|---|---|
| Below 30% | Too dry. You want a humidifier, not a dehumidifier. |
| 30–50% | Leave it alone. This is the target band. |
| Above 50–55% | Worth running one, if the room is warm enough for it to work. |
| Above 60% for weeks | Definitely act — mould can establish in 24–48 hours at this level. |
The target is 30–50% relative humidity, which is what ENERGY STAR recommends year round. Running a dehumidifier through a dry winter down to 25% doesn’t make your house healthier. It cracks your woodwork and costs you money.
My honest position: switch it off in November and put a hygrometer where it was. If the number stays in the 30s and 40s, leave it off until spring. Most people in cold climates could do that and never notice.
Where a dehumidifier in winter genuinely earns its keep
Four cases where the answer flips:
Basements and cellars. Below ground, the walls and floor stay cold and there’s no useful ventilation — opening a window rarely brings drier air in. Basements often run humid all year while the rest of the house dries out.
Crawl spaces. Same reasoning, worse access.
Drying laundry indoors. Every load puts one and a half to two litres of water into the air, and in winter you can’t open the windows to get rid of it. This is the strongest winter case there is, and it’s covered properly in the laundry guide.
Coastal and mild-damp climates. Plenty of places have wet, mild winters rather than cold dry ones. If your outdoor air is 90% at 8°C, ventilation isn’t going to help you.
What to run in a genuinely cold space
If the room is going to sit below about 15°C all winter, stop trying to make a compressor unit work and buy the right tool.
A desiccant dehumidifier uses a moisture-absorbing rotor rather than a cold coil. Nothing freezes, so there’s no defrost cycle to lose time to, and it works down to around 1°C / 34°F. It also puts a little heat back into the room as it runs, which in a cold garage is a bonus rather than a cost.
That’s the answer for unheated garages, outbuildings, boats and caravans. The full comparison — including where a desiccant unit is the wrong choice — is in the garage guide.
Frequently asked questions
Should I run a dehumidifier in winter?
Only if the humidity says so. Measure for a week: below 50% leave it off, above 55% and in a warm enough room, run it. Most heated homes get drier in winter, so the honest answer for many people is no.
Why is my dehumidifier not collecting water in winter?
Because the room is too cold. Below about 18°C output drops sharply, and below 5°C the coil frosts faster than the defrost cycle can clear it — so the compressor stops and the fan runs. That’s protection, not a fault.
Can I use a dehumidifier in an unheated garage in winter?
Not a compressor one, realistically. Buy a desiccant model, which works down to around 1°C because it doesn’t rely on a cold coil.
What humidity should I keep my house at in winter?
Between 30% and 50%. Below 30% and timber, floors and furniture start drying out and cracking; above 60% you’re on the clock for mould.
Will running a dehumidifier in winter save on heating?
Marginally, and not for the reason usually given. Drier air feels slightly warmer at the same temperature, and both types of dehumidifier return their waste heat to the room. It’s a small effect, not a heating strategy.
Should I leave the dehumidifier on in an empty house over winter?
In a basement or a damp property, yes — set it to 50%, make sure it’s draining continuously rather than into a tank, and check the drain line can’t freeze and split.
Related guides: Dehumidifier fan runs but the compressor doesn’t · Dehumidifier for garage · Dehumidifier for drying clothes
Sources
- GE Appliances — Dehumidifier: Ideal Operating Conditions — the operating temperature limits and frost behaviour.
- ENERGY STAR — Dehumidifiers — the 30–50% relative humidity target band.
- US EPA — Mold Course, Chapter 2 — moisture control and why sustained high humidity matters.
Where this guide and your appliance’s own manual disagree, follow the manual. And if your machine has been running fan-only in a freezing garage since December — it isn’t broken, it’s just in the wrong room. Bring it inside and it’ll start collecting again.
