How to choose a dehumidifier for a damp basement
Why a '50-pint' unit today can equal an old '70-pint' one, how to avoid emptying a bucket twice a day, and what cold basements do to dehumidifiers.
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A dehumidifier is one of the few appliances where buying the right size matters more than buying the right brand. Too small and it runs nonstop without ever getting the room dry. The confusion usually starts with the number on the box.
First, measure the problem
Buy a cheap digital hygrometer before you buy a dehumidifier. It shows relative humidity (RH), and it tells you whether you have a problem and later whether the fix is working.
The EPA recommends keeping indoor humidity below 60%, and ideally somewhere between 30% and 50%. Basements commonly sit well above that in summer, which is when mold and that musty smell take hold.
If you can see water on the floor or running down walls, a dehumidifier is treating a symptom. Check gutters, downspouts, soil grading and plumbing first.
The pint rating changed in 2019
Dehumidifiers are rated by how many pints of water they remove per day. In 2019 the U.S. Department of Energy changed the test conditions to a cooler, more realistic 65 °F at 60% RH, replacing the older test at 80 °F.
Cooler air holds less water, so the same machine now earns a smaller number. Roughly speaking:
| Older rating (pre-2019) | Current rating (2019 standard) |
|---|---|
| 70 pints | about 50 pints |
| 50 pints | about 35 pints |
| 30 pints | about 20–22 pints |
This matters when you read older reviews or advice that says "get a 70-pint for a basement". Today that's usually a 50-pint (2019 DOE) model. Look for which standard a listing uses; most current listings mention it.
Sizing in plain terms
Manufacturer charts vary, but the practical pattern is:
- Small, slightly damp rooms: the smallest class (around 20–22 pints).
- A typical damp basement: the mid-to-large class (35–50 pints).
- Large, very damp or wet-smelling basements: a 50-pint unit, or a ducted whole-basement dehumidifier.
When in doubt, size up. A larger unit reaches the target humidity faster and then cycles off, which is quieter and easier on the machine than a small unit running all day.
Drainage decides how much you'll love it
Emptying a bucket gets old fast. In humid weather a large unit can fill its bucket more than once a day.
- Gravity drain hose: most units have a hose outlet. If the dehumidifier can sit higher than a floor drain, the water simply runs out. This is the simplest setup.
- Built-in pump: pumps water up and away, for example into a laundry sink or out a window. Check the rated lift height in the specs against where the water needs to go.
- Bucket only: fine for a small room you check daily, frustrating anywhere else.
Cold basements: auto-defrost matters
Standard dehumidifiers work by cooling air over a coil. In cool rooms, roughly the low 60s °F and below, that coil can frost over and stop removing water. Look for:
- Auto-defrost, which pauses to melt ice and resume.
- A stated minimum operating temperature in the manual.
- For spaces that stay genuinely cold, desiccant dehumidifiers, which don't rely on a cold coil and keep working at lower temperatures.
Features worth paying for
- Auto-restart after a power outage, so it doesn't sit off for days after a storm.
- A built-in humidistat you can set to a target like 50%, so it isn't running when it doesn't need to.
- ENERGY STAR certification. Dehumidifiers can run for many hours a day; efficiency shows up on the power bill.
- A washable air filter that's easy to reach, and wheels with a handle if you'll move it.
Questions people ask
What humidity should I set my basement dehumidifier to?
Somewhere around 45–50% is a common target. Going much lower costs energy without much benefit.
Should a dehumidifier run all the time?
It should run until it reaches your target humidity and then cycle on and off. If it never shuts off, it may be undersized, the space may be too cold, or water is getting in faster than it can remove it.
Where should I put it in the basement?
Near the dampest area, away from walls so air can circulate, and close enough to a drain that you can use the hose. Keep doors to the rest of the house closed so it isn't trying to dry the whole home.