Updated July 2013
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Dehumidifiers improve air quality

Dehumidifiers remove excess moisture from the air, which is a common problem during summer in basements, crawl spaces, storage areas and homes without air conditioning. A relative humidity above 50 percent makes a home's environment feel uncomfortable and can promote the growth of allergy-triggering mold and mildew. Although dehumidifiers are most often used during warm months, the U.S. Environmental Protection Agency (EPA) also recommends keeping the relative humidity in your home between 30 and 40 percent in the winter to prevent condensation from forming on windows.

A dehumidifier uses a fan to blow humid air over a set of chilled coils. This condenses the moisture in the air into water, which is then drained into a collecting basin or hose. The air that returns to the room is both drier and warmer. Manufacturers classify dehumidifiers by the maximum amount of moisture they can extract from the air in a 24-hour period. Home dehumidifiers generally have a capacity in the range of 30 to 70 pints per day, although a few models can remove more than 100 pints of water daily.

Most dehumidifiers have a container to collect the condensed water, which needs to be emptied by hand. When the container is full, the unit will automatically turn off. If you cannot empty the container regularly, consider models with a hose hookup which allows you to connect a hose to a floor drain, removing the condensed water continuously.

A few models are equipped with a pump to expel the water into to a sink or out a basement window. These allow the unit to run without interruption until the desired humidity level is reached, which may not be possible with a collection container. If you can't hook up a drainage hose, you can choose a model with a larger collection container that won't need to be emptied as frequently, but bear in mind it will be heavy when full.

To identify the best dehumidifiers, we evaluated thousands of owner-written reviews across retail websites, such as Amazon.com and Walmart.com. We also consulted both expert and owner-written reviews at specialty retailers, such as AllergyBuyersClub.com, which sells products designed to make life easier for allergy sufferers, DehumidifierExperts.com, Sylvane.com and AchooAllergy.com. ConsumerReports.org evaluates 17 dehumidifiers in its latest round of testing, and Good Housekeeping also makes recommendations for a variety of models.

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