Winter dehumidifying usually makes sense only if your indoor humidity stays above 50 percent

Winter air is naturally dry, so most homes do not need a dehumidifier running during cold months. However, if your basement, bathroom, or kitchen stays damp even when outdoor temperatures drop, or if you notice condensation on windows and walls, your indoor humidity may be high enough to warrant one. The key is measuring first: use an inexpensive humidity meter (available at hardware stores for $10 to $20) to check your actual levels before deciding to run the unit.

Humidity above 50 percent indoors during winter can promote mold growth, dust mites, and musty odors — especially in basements and crawl spaces where air circulation is poor. If your meter shows levels consistently above that threshold, a dehumidifier can help. If humidity stays below 40 percent, running one will only dry out your home further, which can crack wood, damage furniture, and irritate skin and sinuses.

Key Takeaways

  • Check your indoor humidity with a meter before running a dehumidifier in winter; levels above 50 percent warrant use, while levels below 40 percent mean you should leave it off.
  • Basements and bathrooms are the most common winter problem areas because they trap moisture from groundwater seepage, plumbing, and poor ventilation.
  • Running a dehumidifier in winter costs more to heat your home, since the unit generates heat as it removes moisture, but the trade-off may be worth it if mold or condensation is visible.
  • Fixing the source of moisture — improving ventilation, sealing leaks, or running exhaust fans — often works better than running a dehumidifier year-round.

Why winter humidity happens in some homes but not others

Winter moisture usually comes from specific sources rather than outdoor air. A basement with a high water table or cracks in the foundation will stay damp no matter how cold it is outside. Bathrooms without exhaust fans trap steam from showers. Kitchens without range hoods accumulate moisture from cooking. Crawl spaces with exposed soil release ground moisture continuously. If your home has good insulation and air sealing, indoor humidity can actually rise in winter because you are not exchanging indoor air with dry outdoor air the way you do in summer with open windows.

Homes built before 1980 often have this problem because they were not sealed as tightly as modern construction. Newer homes with tight envelopes and mechanical ventilation systems (like ERV or HRV units) usually maintain balanced humidity without a dehumidifier. If you live in a humid climate like the Southeast or Pacific Northwest, winter humidity is more likely than in dry climates like the Southwest.

The cost of running a dehumidifier in winter versus other seasons

A dehumidifier uses 300 to 700 watts depending on size and model. Running one continuously costs roughly $20 to $50 per month in electricity, depending on your local rates and the unit's efficiency. In winter, the real cost is higher because the dehumidifier generates heat as it works, which means your furnace or heat pump has to work less — but the dehumidifier is less efficient at producing that heat than your heating system is. The net effect is a 10 to 20 percent increase in total heating costs if you run it constantly.

If you run the dehumidifier only in problem areas (a basement or bathroom) for 8 to 12 hours per day rather than 24 hours, the cost drops to $5 to $15 per month. Many people find this trade-off acceptable if it prevents mold or stops condensation on windows. If humidity is only slightly elevated, fixing the source of moisture is usually cheaper than running the unit all winter.

Basements and crawl spaces: the most common winter problem

Basements are the number-one place where winter dehumidifying makes sense. Groundwater seepage, cracks in the foundation, and poor air circulation create a naturally damp environment. If your basement humidity reads above 55 percent in January, a dehumidifier can prevent mold on stored items, musty smells, and damage to wood framing. Many people run a dehumidifier in the basement only during winter months when the outdoor air is too dry to help with ventilation.

Crawl spaces are similar: they sit directly on soil and have almost no air movement. If you have a crawl space, installing a vapor barrier over the soil and running a small dehumidifier there can prevent rot in floor joists and rim board. Basement and crawl space dehumidifiers often run smaller and more efficiently than whole-home units because they are not trying to condition a large space.

Bathrooms and kitchens: when to use a dehumidifier instead of a fan

A bathroom exhaust fan is the first line of defense against winter humidity. If your bathroom has one and you run it during and for 20 minutes after every shower, you probably do not need a dehumidifier. However, if your bathroom has no exhaust fan, or if the fan is blocked or broken, humidity will accumulate. A small dehumidifier (20 to 30 pints per day) can handle a single bathroom and costs less to run than a whole-home unit.

Kitchens with gas stoves or frequent cooking can also build up moisture in winter, especially if the range hood is missing or vented into the attic instead of outside. Before buying a dehumidifier, check whether your exhaust fans are working and whether they are vented to the outside (not into the attic or crawl space, which just moves the problem). If fans are working properly, a dehumidifier is usually unnecessary.

Fixing the source of moisture instead of running a dehumidifier

The most cost-effective solution is to stop moisture at the source. In a basement, this means sealing cracks, installing a sump pump, grading soil away from the foundation, or adding interior or exterior drainage. In a bathroom, it means installing or repairing an exhaust fan. In a kitchen, it means venting the range hood outside. In a crawl space, it means installing a vapor barrier and ensuring vents are open in winter (or installing a crawl space dehumidifier on a timer).

These fixes cost more upfront —$200 to $2,000 depending on the problem — but they eliminate the need to run a dehumidifier indefinitely. If you rent, you may not be able to make these changes, so a portable dehumidifier becomes a practical short-term solution. If you own your home and the humidity problem is chronic, fixing the source usually pays for itself within a few years in avoided electricity costs and prevented damage.

Humidity levels to watch for in winter

Indoor humidity between 30 and 50 percent is considered healthy and comfortable. Below 30 percent, air feels dry, wood shrinks, and static electricity becomes annoying. Above 50 percent, mold and dust mites thrive. In winter, aim for 35 to 45 percent if possible — this is dry enough to prevent mold but not so dry that it damages materials or causes discomfort.

If your humidity meter shows 60 percent or higher in winter, you have a moisture problem that needs attention. If it shows 50 to 60 percent, a dehumidifier may help, but fixing the source is still the better long-term choice. If it shows below 40 percent, do not run a dehumidifier; instead, consider adding moisture with a humidifier or by improving ventilation to bring in some outdoor air.

Frequently Asked Questions

Will a dehumidifier make my heating bill go up?

Yes, but usually by 10 to 20 percent if you run it continuously. The dehumidifier generates heat as it removes moisture, so your furnace does less work — but the dehumidifier is less efficient at heating than your furnace is. Running it only in problem areas or on a timer reduces the cost.

Can I use a dehumidifier in an unheated garage or shed in winter?

Not effectively. Dehumidifiers work poorly in temperatures below 50 degrees Fahrenheit. If your garage or shed is unheated, moisture will condense faster than the dehumidifier can remove it. Improve ventilation or add insulation and heat instead.

Should I run my dehumidifier 24/7 or on a schedule?

A schedule is cheaper and usually sufficient. If humidity is only slightly elevated, running the dehumidifier 8 to 12 hours per day (or only when humidity exceeds 55 percent) saves electricity while still controlling mold and odors. Use a built-in humidistat or a plug-in timer to automate this.

What size dehumidifier do I need for a basement?

A 30 to 50 pint-per-day unit handles most basements up to 1,000 square feet. Larger basements or very damp spaces may need 70 pints per day. Check the manufacturer's coverage area on the box, and remember that a slightly oversized unit is more efficient than one that is too small.

Is a dehumidifier better than opening windows in winter?

No. Opening windows brings in dry outdoor air, which naturally lowers indoor humidity at no cost. However, this also lets heat escape, so it works best for short periods — 15 to 30 minutes after a shower or cooking. If you cannot open windows (or if outdoor air is humid), a dehumidifier becomes necessary.