What Size Dehumidifier Do You Need?

May 05, 2024

Here's how to pick the right unit for your space

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The right size dehumidifier can help dry out damp spaces in your home and keep them free of mold, which can break down structural wood and gypsum board and pose health risks to people with sensitivities. The wrong size dehumidifier? Put simply, it won’t get the job done—and it could leave you with a wet, uncomfortable area that becomes a breeding ground for mold, dust mites, and mildew.

• Humidity and Dehumidifiers• When to Get a Large-Capacity, Medium-Capacity, or Small-Capacity Dehumidifier• Sizing Chart• Other Solutions• Highly Rated Dehumidifiers

Read on for tips on how to choose the right size dehumidifier. Below them, you’ll find reviews of some of the top-performing units from our dehumidifier ratings of more than 50 models. And carve out time to consult our dehumidifier buying guide to learn more about the different types of dehumidifiers and how we test them in our labs.

First, determine the square footage of the area you want to dehumidify. Then, pinpoint how damp it really is. A hygrometer, a device that measures a room’s relative humidity, is helpful for that second task. You can find one for less than $10.

In warmer weather, the ideal relative humidity in a living space is 40 to 60 percent. In cooler weather, it’s 30 to 50 percent.

Lower temperatures, such as those in basements, can fool you into thinking a room is less humid than it is, says Trey Lewis, a heating, ventilation, and air conditioning technician who created HVAC Training Shop, a blog for home and commercial HVAC contractors. That’s why you use a hygrometer. “It gets a baseline of what you’re really working with,” Lewis says.

If the area is large—1,200 square feet or more—determining the right size dehumidifier is a no-brainer. Whether the room just feels slightly damp or there’s noticeable condensation, you’ll need a powerful unit to dry the air. Large-capacity dehumidifiers can fill that need in all but the wettest situations.

The maximum amount of water that such a unit will remove is usually 50 to 60 pints per day. When a dehumidifier is collecting so much water, it’s useful to have the water flow directly into a drain rather than having to empty the tank. Typically, dehumidifiers include a hose coupling so that you can attach a standard garden hose and let the water run into, say, a floor drain in your laundry room or a walk-in shower drain. Models with a pump let you move the water higher than the dehumidifier to empty into, say, a laundry sink—a lot easier than lugging a full tank of water to the nearest drain.

Most of the dehumidifiers in CR’s ratings don’t have a pump. But Misha Kollontai, the CR engineer who leads our dehumidifier testing, says similar models are often available with pumps for about $30 more.

Pro tip: In a very big space, you might also want to post a fan in another part of the room to improve airflow and distribute the drier air. Your dehumidifier’s fan might not be powerful enough for the job, Kollontai says, because these machines are designed to balance fan power and noise mitigation.

Rooms from 600 to just under 1,200 square feet that have small puddles, condensation, or mold need the same attention as a larger space. That means using a large-capacity dehumidifier for them, too, Kollontai says.

If you have an area of 600 to 800 square feet that’s slightly damp or has a musty smell, a medium-capacity dehumidifier may solve your problem.

Wetter rooms as small as 400 square feet can also benefit from midsized units, which are designed to remove 30 to 39 pints of moisture per day.

As a group, medium-capacity dehumidifiers are less noisy than larger models, which is useful when you’re trying to dry out the air in a living area. You’ll typically pay less for this size dehumidifier, but some can cost as much as a large model.

Areas of less than 600 square feet typically call for a small-capacity dehumidifier. In general, they remove less water and are less expensive than medium- and large-capacity models.

In CR’s ratings, the four recommended small-capacity dehumidifiers all nab top marks in our water removal test. They also get strong or excellent ratings for noise—a key feature for closer quarters—and include a built-in fan. Only one has a pump.

One caveat: In a bathroom, Lewis says, installing a good exhaust fan is probably a better way to control humidity than using a small-capacity dehumidifier. “That’ll suck all the moisture out in a few minutes,” he says.

Use this guide to help you choose the right dehumidifier size for your space. These figures—and Consumer Reports’ test results—rely on Department of Energy dehumidifier labeling standards, which were updated in 2019 to more accurately reflect how well they work in basements, where many of these units are used. (You can learn more about them in our dehumidifier buying guide.)

If you can’t find mention of the 2019 standard on the packaging or product information guide, check the model page on the manufacturer’s website. The retailer’s page may also display the information in the product details.

Even the best dehumidifier won’t solve your problem if too much moisture from the outside is continually seeping into your home. Unclogging gutters and making sure downspouts are directing rainwater at least 5 feet from the house can make a huge difference. If puddles and water droplets on floors, walls, and windows remain or worsen, contact a water remediation expert, an HVAC contractor, or a business that seals basements from moisture.

If there’s too much moisture in most rooms in your house, you may be better off with a whole-house dehumidifier. (Consumer Reports doesn’t test these.) Whole-house dehumidifiers are available as portable units or as add-ons to an existing central heating and air conditioning system. Manufacturers say they can handle an area up to 5,000 square feet. These units are expensive, but because they remove so much moisture from the air, they could enable you to cut back on air conditioning.

In some instances, you may need more than one solution, Lewis says. For example, if your basement flooded, you’ll need to first remediate the damage and remove all the water, and then install a dehumidifier to keep residual moisture at bay.

For musty crawl spaces—areas prone to mold growth—you might need an industrial-sized dehumidifier that can remove 70 or more pints of water per day. You can buy one yourself or through a contractor. These units typically have no tanks, so you’ll need to attach a drain line, Lewis says. For proper airflow, you also may need specialized ducts. Unless you’re handy, leave those tasks to a professional.

Once you have a dehumidifier up and running, it’s a good idea to check humidity levels again, Kollontai says. On many dehumidifiers, you can see the room’s relative humidity in the unit’s built-in digital display, but it’s also a good idea to use that hygrometer you bought to take readings in different areas of the room, to make sure the humidity is evenly distributed.

“If at full power your dehumidifier is only pulling your humidity down to 60 or 70 percent, you need a bigger dehumidifier,” Kollontai says.

Below, we share some of the highest-rated dehumidifiers in different sizes, based on CR’s lab tests. For more great options, check out our picks of the best dehumidifiers.

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