Dehumidifiers for basements and damp rooms: compare models

Each number in the finder comes from EPA’s list of ENERGY STAR certified dehumidifiers, which gives the capacity and efficiency measured under the U.S. Department of Energy’s test, and the yearly energy use.¹

Why humidity matters for allergies

EPA’s mold guide says there are many types of mold, and none of them will grow without water or moisture.⁴ The CDC advises keeping indoor humidity as low as you can, no higher than 50%, all day long, and says an air conditioner or dehumidifier will help keep the level low.⁵

A practice parameter from US allergy societies says that once humidity drops below 50%, dust mites multiply less and survive less well.⁶ The same parameter notes that in a series of studies in England, free-standing dehumidifiers were ineffective, and whole-house dehumidification lowered mite allergen but not symptoms, while US studies using more extensive measures lowered live mites and mite allergen.⁶ AAAAI says the humidity level in a house should be kept between 40 and 50%.⁷

ENERGY STAR says the optimum indoor relative humidity is generally considered to be 30% to 50%, and that levels above that may promote mold growth.² In colder climates during the heating season, it suggests 30% to 40% to prevent condensation on windows.²

What the numbers mean

Capacity. The list gives each model’s capacity in pints of water removed per 24 hours. For portable models the figure represents expected performance in a basement, and for whole-home models in the average home.¹³

Older ratings. ENERGY STAR says the test changed in June 2019: portable models are now tested at 65°F instead of 80°F, closer to a basement, so they will likely report a smaller capacity. From early 2020, it says, you may see models that look like older ones but have lower capacity ratings.³ For portable models, its rough guide puts an old 50-pint rating at about 30 pints today, and an old 70-pint rating at about 40 to 45, though it says the change for specific models will vary.³

Efficiency and energy use. Efficiency is liters of water removed per kWh, and in general a higher number means a more efficient model.² ENERGY STAR says the measure includes the energy a dehumidifier uses when it has cycled off.³ The yearly figure is the energy used under typical conditions, including fan and standby modes.¹ ENERGY STAR says certified models use 20% less energy than similarly sized conventional units.²

Type. Portable dehumidifiers work inside the space they dry without added ducts; whole-home models are installed with ducts that carry dried air to one or more places in the home. Some can work both ways with a ducting kit.¹ ENERGY STAR says a whole-home unit may be the right choice in a humid climate with central air, and that these systems can be expensive but bring significant benefits to relatively well-sealed homes that see humidity above 55% consistently throughout the house.²

Refrigerant. The list names the refrigerant for nearly every model and, where given, its global warming potential, and it marks the lower-GWP options.¹

Choosing a capacity

ENERGY STAR sizes a dehumidifier by the size of the space and how damp it is without one, and says it’s better to oversize than undersize.² Its chart for estimating the minimum capacity of a portable dehumidifier, in pints a day:

How damp the space is without one	Small to medium room, under 2,000 sq ft	Large room, over 2,000 sq ft
Slightly to moderately damp (50–75% relative humidity)	20–30	30 or more
Very damp (75–90%)	25–40	40 or more
Wet (90–100%)	30–50	50 or more

The table restates ENERGY STAR’s chart.² When replacing a dehumidifier, it suggests judging by how much water you empty each day.² It says whole-home units should be sized and installed by a professional.³

Using one

ENERGY STAR suggests keeping the doors and windows of the space closed while a dehumidifier runs, and placing it away from walls and furniture if the air doesn’t come out of the top.² It advises a grounded outlet and keeping drain hoses away from cords and electrical devices.² It notes that frost can form on the coils below 65°F: for spaces that are often colder it suggests a model specified for lower temperatures, says a frosted unit should be switched off to defrost, and mentions that some models have an anti-frost sensor that turns the unit off when the air gets too cold.² ENERGY STAR says every certified dehumidifier has a built-in humidistat for setting the humidity you want, and if yours doesn’t show humidity levels, it suggests a separate hygrometer near it.²

For basements, ENERGY STAR also points to drainage around the foundation, such as extending downspouts and sloping soil away from the house, which it says may lower basement humidity.² Our guide to allergies at home in winter covers damp spots, mold and dust mites indoors.

What this finder can’t tell you

• It lists only models certified to ENERGY STAR’s current requirements and sold in the US.¹ Dehumidifiers without certification aren’t in EPA’s list, so they aren’t here.
• The capacities and efficiencies are the ones on EPA’s list, from the Department of Energy’s test.¹ We don’t test dehumidifiers.
• It doesn’t show prices, noise or bucket size, and nobody pays for a place in it. Models are listed by brand, A to Z, unless you choose another order.
• It doesn’t check recalls. The U.S. Consumer Product Safety Commission posts product recalls.⁸