Best Dehumidifier by Room Size: 35 Pint, 50 Pint and Crawl Space

For a damp bedroom, office or bathroom, a 35 pint dehumidifier (2019 DOE rating) is enough. For a basement or any room with a musty smell or condensation, buy 50 pints. Makers rate 35 pint units for about 3,000 to 3,500 sq ft and 50 pint units for 4,500 to 5,000 sq ft, but those numbers assume moderately damp air, so size up when in doubt.

In 2019 the DOE moved the test from 80 F and 60 percent humidity to 65 F and 60 percent, which lowers the rated pints for the same machine. A unit sold as 50 pints under the old test is rated about 35 pints under the new one, and an old 70 pint unit is about 50 pints. Midea's 35 pint Cube, for example, is listed as similar to a 50 pint 2012 DOE unit.

About $0.62 a day, or roughly $19 a month, for a typical 50 pint unit. That assumes a 500 W draw, 12 hours a day and the compressor on 60 percent of the time, which is 3.6 kWh a day at the 17.3 cent per kWh US average. In a state at 30 cents per kWh the same use costs about $1.08 a day.

Set it between 30 and 50 percent, the range the EPA recommends for indoor air, and 50 percent is the usual setting for a basement. The EPA advises keeping indoor humidity below 60 percent to limit mold growth. Setting it lower than about 40 percent mostly adds run time and cost.

Only if there is no floor drain lower than the dehumidifier. A gravity drain hose works only downhill, while a built-in pump pushes water up to a sink or out a basement window. Without either, you empty the bucket by hand, which for a 35 pint unit with an 8.5 pint bucket is about 4 times a day at full output.

It is better to use a unit built for crawl spaces. Crawl space units like the AlorAir Sentinel HD55S have auto defrost and low-temperature operation for cool, damp air and drain continuously by hose. Most portables are designed for living spaces, have buckets that would need emptying and lose capacity as the air gets colder.

No, a larger unit in a small room just reaches the set humidity faster and then cycles off. The humidistat stops the compressor at your setting, so you pay for the water removed rather than for the rating. The main trade-offs are a larger footprint and a slightly higher purchase price.

AHAM pints are measured at 80 F and 60 percent humidity, and saturation pints at 80 F and 100 percent humidity. Saturation numbers run about twice the AHAM figure, so the AlorAir Sentinel HD55S is 55 pints AHAM and 120 pints at saturation. Compare crawl space units on AHAM pints.

Yes, slightly. All the electricity it uses ends up as heat in the room, about 1,700 BTU per hour for a 500 W unit, plus the heat released as water vapor condenses on the coil. That is useful in a cool basement but works against an air conditioner in summer living space.

It is worth it when a whole home or a large finished lower level stays humid and you want no buckets or units in the living space. A ducted unit like the Santa Fe Ultra70 removes up to 70 pints a day and filters to MERV-13, but it costs several times a portable and usually needs an HVAC contractor to install. For one or two damp rooms, a portable is the better buy.