Need a dehumidifier? Here’s how to find the right size

If you need a dehumidifier to combat excess moisture in your home, you’ll want to pick one that is effective and highly rated. But how does one know which dehumidifier size and type to purchase? What’s the best dehumidifier for your specific situation? Choosing one can be overwhelming, especially if you don’t want to waste your money. Use this information guide to help you.

Whether you’re looking to take the damp smell out of your basement, or just want to ensure a healthy, mildew-free home, here’s how to select the right size and type of dehumidifier.

Understand what dehumidifier capacity means

Dehumidifiers are usually rated by a single number: the amount of water, in pints, that they can extract from the air within 24 hours. This rating helps determine the humidifier's capacity as well as its suitability for rooms of different sizes and different humidity levels. A small dehumidifier might be able to manage five to 10 pints at a time, while a larger model could manage 60 to 70 pints. Industrial models designed to clear out flooded properties can accumulate hundreds of pints at a time.

These numbers are only an estimate, though—how much the dehumidifier will extract for you will depend on the level of humidity, the temperature, and other factors.

Assess your space

Whether you know how a dehumidifier works or not, know this: Square footage is crucial when selecting a dehumidifier because it determines how much space the unit needs to cover. Larger areas require dehumidifiers with higher capacity.

Before selecting a dehumidifier, you need to figure out how much space you want the dehumidifier to cover. To this end, you'll want to measure the room in your house where you're going to put the device and calculate the square footage. If you plan to use it in a space where two rooms connect—such as a living room and dining room with an open arch—treat the two rooms as one, as the air will flow from one to the other.

The way a room is configured—and how much airflow it has—also impacts the size of the dehumidifier you’ll need. Keep in mind that open spaces allow moisture to be removed more evenly, and placing the unit near a doorway or HVAC vent can help improve moisture removal.

Find your room’s humidity levels

The humidity of a room is a key factor in the growth of mold and mildew, both of which can be dangerous to your home and your health. A room with a high humidity level is a damp environment that’s ideal for mold growth, and once mold starts growing it can produce allergens, irritants, and mycotoxins. A dehumidifier can be the key to ensuring that your home stays mold-free.

The right dehumidifier size for your home depends on the size of the room and its humidity level, which can range from a mildly clammy feel to water dripping down the walls (rarely a good sign). To assess what capacity dehumidifier you need, it’s best to measure the current humidity level in your home. The easiest (and most accurate) way to do this is to purchase a hygrometer, which will give you real-time humidity readings.

Ideally, you want a humidity level between 30% and 50%. This range not only feels the most comfortable—not too dry, not too damp—but it also prevents mold growth. A reading of 50% to 70% is considered high, and anything above 70% is very high and very concerning. For “high” and “very high” readings, you’ll want to ensure that you purchase a dehumidifier with a high capacity, in order to remove as much moisture from the air as possible.

Your basement conditions may be different

Cooler temperatures and higher moisture levels can significantly impact the dehumidifier size and capacity you need.

Standard dehumidifiers that use compressors may not be as effective in cooler environments like a basement or a garage, because they can freeze up. When choosing a dehumidifier for colder rooms, it’s best to opt for a desiccant model that removes moisture from the air by using a substance like silica gel.

When dealing with higher moisture levels—also often found in basements—you’ll need a larger capacity dehumidifier that can handle more moisture. Always take individual humidity readings for each area so that you know which rooms may need a dehumidifier with a higher capacity.

Different types of dehumidifiers: Refrigerant vs. desiccant

The two main types of dehumidifiers—desiccant and refrigeration—have different strengths. Understanding how they work can help you buy the right one for your situation.

In short, desiccant dehumidifiers are best for smaller areas that need fairly consistent dehumidification, like basements or laundry rooms. They don’t use that much energy, so you can leave them running all the time.

Refrigeration dehumidifiers, on the other hand, are better for larger rooms that need occasional dehumidifying on very humid days, but they can use a lot of energy.

Resources

• Science Direct, Study on the influence characteristics of thermal effect of internally cooled dehumidifier
• Condair, Desiccant vs. condensing dehumidifiers
• WikiHow, How to measure relative humidity