How to Choose the Right Dehumidifier for Room Size and Room Type

When choosing a dehumidifier for any room, getting the right size can make all the difference. Dehumidifier size refers to its capacity to remove moisture, typically measured in pints per day or PPD. Standard home dehumidifiers range from 20 to 70 pints per day, which can cover an area from 500 up to 4,500 square feet.

Important note for commercial applications: if you’re looking to dehumidify a commercial space, check out our separate guide on how to size a commercial dehumidifier.

A higher pint capacity comes with a greater square feet coverage, but the same rating between different dehumidifiers doesn’t always mean the same coverage area. When choosing a dehumidifier for any purpose, the size is one of the first things you must consider. The best small dehumidifiers may be easily portable, but if it’s just too small it won’t be effective in removing moisture in the air from the entire space. On the other hand, a large capacity dehumidifier or commercial dehumidifier costs more and uses more electricity – so get something too big and you’ll end up with higher bills.

It’s essential to get just the right size dehumidifier for your particular space. But how do you find the right size?

First, it’s good to know how pint ratings are determined. Manufacturers sometimes provide two sizes for a single dehumidifier. The current rating is almost always lower than the older one. This isn’t because the dehumidifier has been remodeled, it’s only the testing standards that have evolved in order to give customers a more realistic expectation of the performance.

To find the most ideal dehumidifier size for your space, you need at least these two things: the level of dampness in the room, and its square footage. Use this guide to help you choose the right dehumidifier.

Dehumidifier Sizing and Rating Standards

The Department of Energy (DOE) defines dehumidifier performance ratings and the testing standards that determine performance. Starting June 2019, performance ratings are the capacity, in pints per day, and energy efficiency measured by the integrated energy factor (IEF) in liters per kilowatt-hour. Compared to the old energy factor (EF), the IEF is a more accurate representation of the energy consumption in actual use.

The 2012 testing procedures test dehumidifiers at 80°F temperature. As of early 2020, dehumidifiers have new ratings based on the new DOE standards at 65°F. This new condition is supposed to give a more realistic comparison to the dehumidifier’s actual performance in a basement setting. Because of this, the current pint ratings appear lower than the older. A previously rated 30-pint, 50-pint, or 70-pint dehumidifier is now approximated as 22-pint, 35-pint, and 50-pint, respectively. Actual rating varies per model and brand.

How Dehumidifiers Work

There are different types of dehumidifiers classified by the process they use to extract moisture.

Compressor Dehumidifier

This type of dehumidifier uses a compressor to power the condenser and evaporator coils that remove moisture and warm the air. A fan draws the humid air and passes it over the cold coils. The cooler air loses its ability to hold moisture, then water droplets form. This is collected in a tank or pushed out through a hose. To protect the internal components, compressor dehumidifiers stop dehumidifying when frost forms.

Desiccant Dehumidifier

This type uses a desiccant or hygroscopic chemical that absorbs or adsorbs moisture from the air. The main difference from compressor-based dehumidifiers is the desiccant doesn’t cool the air to remove moisture. Moisture clings to the surface of the desiccant when they come in contact with each other. Since a desiccant doesn’t use a compressor, it is lighter and quieter, but typically more expensive and limited in capacity.

Peltier Dehumidifier

Another method that mini dehumidifiers commonly use is the Peltier effect or thermoelectric cooling. It is based on the idea that a voltage of electricity creates a temperature difference between the two sides of a Peltier module. Humid air is drawn by a small fan through the cold side of the unit where moisture condenses. The cold, dry air then passes through the hot side and warmer, dryer air is released. It’s similar to a compressor dehumidifier in terms of operating temperature, but a Peltier dehumidifier has a much smaller capacity, usually between 9 to 25 ounces (250 to 750 ml).

Check the Room’s Humidity Level

The volume of water the dehumidifier has to remove plays an important role in determining the right size you need. Humidity levels that rarely go past 60% will probably require a smaller capacity, while humidity levels around 80% to 90% will need the maximum capacity you can get considering the room size.

If you don’t have a hygrometer to measure the exact values of relative humidity in the room, watch out for the common signs of excess moisture. Damp and musty air is the first sign of humidity. The more severe the dampness, the higher capacity you need. You may also notice condensation on windows and walls or damp spots on floors. In extreme cases, you’ll see mold growing on wall corners, under sinks or toilets, beneath carpeting, or almost any moist surface.

Keep in mind that a full bathroom where people are taking showers often has a much higher moisture load per square foot compared to a bedroom. Bathrooms also have less space to work with so the best bathroom dehumidifier will likely be different than the best dehumidifier for a bedroom.

Measure the Room’s Size

It’s important to know the exact room size or the square footage of the space to be sure that your dehumidifier can cover every corner. Multiply the length and width of the room to get the area in square feet or square meters. Alternatively, multiply the length, width, and height to get the volume in cubic feet or cubic meters. Manufacturers usually indicate either one or both, so it’s best if you know the two beforehand. In spaces with irregular shapes, ask an indoor environmental professional for help. 

two men measuring a room to size a dehumidifier

Dehumidifier Sizing Chart

What size dehumidifier do I need for a 500 square feet space? Based on this guide by Energy Star, you will need at least a 10-pint dehumidifier for a moderately damp area (50-60% relative humidity). For a very damp 500 sq ft. space (60-70% RH), add at least three more pints. For an area of 1,000 sq. ft, find at least a 14-pint dehumidifier, adding four more pints. Likewise, add four pints for every additional 500 sq ft area, and three pints for more severe dampness.

Dehumidifiers do not come with these exact values for the capacity. The lowest capacity rating for most brands is 20-pint or 22-pint. The next bigger size would be 30-pint or 35-pint. The highest capacity for portable dehumidifiers is usually 50 pints (previously 70 pints under the DOE 2012 standards), but some brands still offer 70-pint units for spaces 4,500 square feet and larger.

Once you find the square footage of your space and the recommended dehumidifier capacity, round up the value to the nearest available size for maximum efficiency. For example, get a 20-pint dehumidifier for a very damp 500 square feet space, and a 22-pint to 30-pint dehumidifier for a similarly damp 1,000 square feet room. For a 1,000 square feet to 1,500 square feet area, get a 20-pint dehumidifier at least.  And for a 1,500 square feet to 2,000 square feet space, start with a 30-pint dehumidifier. 

Consider the following table as a guide:

Square Footage500 sq ft1,000 sq ft1,500 sq ft2,000 sq ft2,500 sq ft
Moisture LevelRecommended Dehumidifier Capacity
Moderately Damp<20 pints20 pints20-25 pints30 pints30-35 pints
Very Damp20 pints20-25 pints25-30 pints30-35 pints35-40 pints
Wet20 pints25-30 pints30-35 pints35-40 pints40-45 pints
Extremely Wet20-25 pints30 pints35-40 pints40-45 pints45-50 pints

Since this is a common topic, we’ve put together a specific guide to that covers the best small room dehumidifiers, as well as the best dehumidifiers for bathrooms. Additional guides for home dehumidifiers can be found here.

Other Factors to Consider When Choosing Dehumidifier Size

Generally, most dehumidifiers perform better in higher temperatures. Compressor units, in particular, are ideal for hot and humid climates above 60-65°F. Below this temperature, frost may start to form on the inside and damage the components. Although, some low temperature dehumidifiers are specially designed to operate effectively in temperatures as low as 41°F. 

To prevent condensate freezing on the coils, auto defrost is a standard feature in modern dehumidifiers. If you need to operate at 41°F and below, your best option is to find a desiccant dehumidifier. The caveat is a full-size desiccant costs a lot more for a smaller size and draws more power on operation.

Also consider the source of moisture in the room. For every three or more occupants, add five pints to the capacity. Household tasks like showering, cooking, and washing and drying laundry will increase humidity. Areas like crawlspaces and basements tend to be cooler and damper than other areas of the house. If you notice visible mold and mildew, you may need a more powerful dehumidifier.

Outdoor conditions can affect the indoor environment as well. If you live in a region with high relative humidity, expect a humid climate in most seasons. Take all of these factors into account to get the right size dehumidifier. With proper care and maintenance, this will help maximize the efficiency of your appliance.

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