How to Prepare a Dehumidifier for Winter Storage

Why winter storage matters

Dehumidifiers often work hardest in warm, humid months and sit idle when indoor humidity drops. That idle period is exactly when moisture left inside can cause problems. The Environmental Protection Agency (EPA) notes that molds reproduce by tiny spores that float in the air and begin growing when they land on wet surfaces. If you store a dehumidifier with standing water in the bucket or a damp interior, you risk mold growth on the tank, coils, and fan.

The Centers for Disease Control and Prevention (CDC) recommends keeping indoor humidity no higher than 50% to discourage mold. A dehumidifier that is not properly dried can actually become a source of moisture and mold spores. Taking the time to prepare the unit correctly protects your investment and ensures it runs cleanly next season. For a broader look at seasonal care, see our guide on seasonal storage.

Step 1: Unplug and drain completely

Start by unplugging the dehumidifier from the outlet. Remove the bucket and pour out any remaining water. If you used a continuous drain hose, disconnect it and let the hose drain completely. For models with a built-in pump, check the user manual for how to drain the pump reservoir; many have a small cap or valve that releases the remaining water. A helpful resource is our pump maintenance guide.

Do not overlook the water that stays in the condensate tray or on the coils. Tilt the unit backward and forward slightly to help trapped water run out. The EPA advises drying water-damaged areas and items within 24 to 48 hours to prevent mold, so draining should be done promptly. If you have a hose that runs to a floor drain, make sure the hose is empty and dry before storing it separately.

Step 2: Clean the bucket and filter

Wash the bucket with warm soapy water, rinse it, and dry it with a clean cloth. If you see any mold, you can use a bleach solution. The CDC suggests a mix of no more than 1 cup of household laundry bleach in 1 gallon of water to remove mold from hard surfaces. Never mix bleach with ammonia, and always work in a ventilated area. For more detailed guidance on removing odors and buildup, see our bucket cleaning and odor removal guide.

Remove the air filter and clean it according to the manufacturer's instructions. Some filters are washable, while others are replaceable. A clogged filter reduces airflow and can leave dust and debris that trap moisture. Let the filter dry completely before you store it. If you are unsure whether your filter is washable, check our filter maintenance guide.

Step 3: Dry the interior

After cleaning, wipe down all accessible surfaces with a dry cloth, including the bucket well, the interior walls, and the fan blades. If your unit has a fan-only mode, you can run it for an hour or two to circulate air through the system and help evaporate leftover moisture. If not, leave the unit unplugged with the bucket removed and the filter out for at least 24 hours in a dry room.

The goal is to remove as much moisture as possible before storage. The EPA's key to mold control is moisture control, so a thoroughly dried unit will not support mold growth. Pay special attention to the area around the evaporator coils, where frost and condensation often collect. For additional tips on dealing with frost buildup, see our auto-defrost explanation.

Step 4: Clean coils and interior (if needed)

Inspect the evaporator coils for dust, dirt, or mold. Use a soft brush or a vacuum with a crevice tool to remove loose debris. For disinfecting, you can apply the same bleach solution the CDC describes, but do so carefully. Wear gloves and goggles, open windows, and avoid saturating electrical parts. For a deeper explanation of coil cleaning, you can refer to our internal coil cleaning guide.

If you notice heavy buildup, a coil-cleaning spray designed for dehumidifiers is an option, but always follow the product instructions. After cleaning, dry the area thoroughly and allow the unit to air out for another day. Do not use a pressure washer or submerge the unit. If your unit has a removable drain pan, clean that as well to prevent mold from developing in a hidden area.

Step 5: Check the power cord and connections

Before storing, inspect the power cord for cracks, fraying, or exposed wires. If you find any damage, replace the cord or take the unit to a qualified service person. Also check the drain hose and any adapters for cracks or blockages. A damaged hose can leak during the next season and cause water damage.

If your dehumidifier has a pump, verify that the pump inlet and outlet are clear. A quick rinse with clean water and a dry cloth can prevent mineral buildup. If you used an extension cord during operation, make sure you store it separately and never coil it tightly around the unit. For more on electrical safety, see our extension cord safety guide.

Step 6: Choose a storage location

Store the dehumidifier in a dry, well-ventilated space, such as a closet shelf, a basement shelf away from damp walls, or a heated part of the home. Avoid attics or garages where temperature swings can cause condensation inside the unit. Keep the unit upright to prevent oil from migrating out of the compressor. If you must store it in a cooler area, place it on a raised platform to reduce the chance of moisture pooling underneath.

Cover the unit with a cloth or the original box to keep dust off, but do not seal it in plastic. If you have a drain hose, coil it separately. When spring arrives, inspect the unit before plugging it in. See our after-storage checklist for a quick verification routine. If you are considering a new unit, our best dehumidifiers for basements guide can help you pick the right capacity.

What to pick for your use next season

Questions

Should I leave the bucket inside the dehumidifier during storage?

No. Always remove and clean the bucket, then store it separately. Leaving water in the bucket invites mold and can warp the bucket over time. For more on bucket care, see our bucket cleaning guide.

Can I store my dehumidifier in an unheated garage?

It is not ideal. Cold temperatures can cause condensation and potential frost, and freezing may damage internal components. The EPA and CDC emphasize moisture control; a dry, temperature-stable location is safer. If you must use a garage, place the unit on a shelf and cover it with a breathable cloth.

How long should I let the dehumidifier dry before storing?

At least 24 hours. The EPA says mold can begin growing within 24 to 48 hours on wet surfaces. Allowing a full day of air drying gives trapped moisture time to evaporate. In humid climates, you may need to extend that to 48 hours.

Do I need to clean the coils before winter storage?

If you see dust or mold, yes. A clean coil operates more efficiently and reduces the chance of organic growth. Use a soft brush and, if needed, a bleach solution as described by the CDC. For step-by-step instructions, see our coil cleaning guide.

Should I run the dehumidifier after winter storage to test it?

Yes. After a full dry-down, plug it in and run it for a few minutes to verify the fan and compressor work. Check the bucket and filter before running. This can be done in a laundry room or basement. If you notice issues, consult the manufacturer's troubleshooting guide. For a thorough checklist, see our after-storage guide.