Dehumidifiers

How to choose a basement or crawl space dehumidifier

A dehumidifier pulls water out of the air so a space stays dry enough to discourage mold, musty smells and dust mites. The U.S. EPA advises keeping indoor relative humidity below 60%, ideally between 30% and 50%. A basic hygrometer (humidity meter) tells you where your space is before and after.

Capacity: pints per day

Capacity is the amount of water a unit can remove in a day, listed in pints. Larger and wetter spaces need more. Use the coverage area the maker states, and size up if the space is very damp, smells musty or has had standing water. Since 2019 the U.S. Department of Energy rates capacity at 65°F and 60% humidity instead of 80°F, so newer ratings can read lower than older labels for a similar machine. Compare ratings made under the same standard.

Drainage: bucket, hose or pump

Small units collect water in a bucket you empty by hand. For a basement or crawl space you will usually want continuous drainage: a hose to a floor drain or sump (gravity) or a built-in condensate pump that pushes water up and out to a sink or the outside. If the drain point is higher than the unit, check the pump’s stated lift height and hose length.

Cool spaces need low-temperature operation

Basements and crawl spaces are often cool, and the cold coil inside a dehumidifier can frost over. Look for automatic defrost and the lowest operating temperature the maker lists, and compare it with how cold your space gets in winter.

Fit, installation and access

Crawl space models are usually low and compact so they fit through access openings, and many can be hung from floor joists or set on risers to stay off the ground. Leave room to reach the filter and the drain. Outlets in crawl spaces and unfinished basements generally need GFCI protection under the U.S. electrical code, so check yours. A dehumidifier works best in a space that is sealed from outside air, for example with a vapor barrier on a crawl space floor.

Filters

Most units have an air filter in front of the coil to keep dust off it. Some are washable; others are replaceable pleated filters, often rated by MERV. Before buying, check that replacement filters for that model are easy to get and how often the maker says to change them.

Energy use and controls

A dehumidifier in a basement can run many hours a day, so efficiency matters. ENERGY STAR certified models meet efficiency limits set by the U.S. EPA, and efficiency is listed as an integrated energy factor (liters of water removed per kWh; higher is better). A built-in humidistat that shuts the unit off at your target humidity, a remote sensor or controller, auto-restart after a power cut, and a stated noise level are all worth comparing.

Quick checklist

• Capacity and coverage that fit your space and how damp it is
• Continuous drainage, with a pump if the drain point is higher
• Low-temperature operation with automatic defrost
• Size that fits the access opening, with hanging or riser options
• Easy-to-find replacement filters
• Efficiency rating, humidistat and auto-restart
• Warranty terms from the seller or maker