What Size Dehumidifier Do I Need for Basement?

Basement Dehumidifier Size Chart

Basements are the source of dampness in most homes. It’s the place that needs a dehumidifier the most as you will be controlling the humidity right from the source. However, when getting the unit, you will need to answer the question ‘what size dehumidifier do I need for the basement?’

There is no specific size to fit the different basement sizes. However, you can estimate the dehumidifier size, but you will need to know how big your basement is. If your space is 500 square feet and averagely damp, pick a 10-pint dehumidifier. Add four pints to the unit’s capacity for an additional 500 square feet.

However, there is more to sizing a dehumidifier than the above estimation. Remember, sizing the dehumidifier ensures you get an ideal unit capable of pulling all the unwanted water from your basement to prevent damages and a size that won’t consume much energy. This post will take you through the steps you can use to size the dehumidifier you need for your basement.

How to Size a Dehumidifier for Your Basement

With basements known to cause high humidity levels in most homes, many people are unaware that they need to make sure their dehumidifier is appropriately sized for their basement. If you do not properly size your dehumidifier, it is possible that it won’t be powerful enough to keep the humidity level down in your basement. On the other hand, if you choose a unit that’s too big for your basement or home, this could result in using more electricity than necessary and possibly overloading the system.

There is no one specific dehumidifier size that can fit all basements. The simplest way of determining the size of your space needs is by calculating the room size, determining the dampness level, and crossing this with the room dampness in the dehumidifier sizing chart provided here. Let’s jump right in!

Determine the Dampness Levels in Your Basement

Before you purchase a dehumidifier for your basement, you’ll need to get an idea of how damp it is. The easiest way to do this is with a quality humidity meter. Test the humidity levels in a couple of different spots in your basement and then average them out to get a more accurate reading.

Also, take note of any visible signs of moisture or standing water. This will come into play later when you decide on the size dehumidifier you’ll need for your basement. The dampness level will also help determine if you need a portable dehumidifier or a whole-house model.

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The table below shows the various dampness levels to watch for when sizing a dehumidifier.

Humidity Level (%)Environment ConditionHow it feels
50-60Moderately DampThe air feels damp, heavy, or clammy – you can start to notice must odor
60-70Very DampThe space feels damp and smells musty – you can start to notice wet spots on the walls and floor
70-80WetThe water beads on the floors and walls or seeps in around the room edges – the area feels and smells damp
80-100Extremely WetThere is standing water on the floor.

Determine the Basement Space Size

The next thing you’ll need to do is get an accurate measurement of the square footage of your basement. This will be very helpful in determining the size dehumidifier that you need to purchase for your central air system.

You’ll need to get out your measuring tape and measure the length and width of the entire basement. If you have a finished basement, take these measurements from wall to wall – this will be your living space. If it’s an unfinished basement, make sure to note whether or not there are any permanent walls or columns in place.

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Determine the Basement and Outdoor Temperatures

Once you have the square footage of your basement, the next step is to determine the average basement temperature and outdoor temperatures. Use a thermostat to keep tabs on the basement temperature levels.

If your basement is extremely cold, you’ll want to make sure you purchase a dehumidifier with enough power to keep up with the cold temperatures. On the other hand, if your basement is only slightly damp but warm, you’ll need to find a unit that’s powerful enough to remove wetness in warmer temps.

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What’s more, the average basement temperatures will also affect the type of dehumidifier you will use. You can either use a desiccant refrigeration dehumidifier or a refrigerant dehumidifier.

a) Desiccant Refrigeration Dehumidifier

A desiccant refrigeration dehumidifier works by moving air over a desiccant or drying agent. This is accomplished with the use of a fan or blower. When the air passes over the desiccant, it removes moisture through condensation. There are two types of desiccant dehumidifiers, the most common being the rotary or wheel type.

b) Refrigeration Dehumidifier

A refrigeration-type dehumidifier moves air over a cold evaporator coil or tube. The coil cools the air and any moisture, causing the water to condense and fall into a bucket. This type of dehumidifier uses the same kind of coils found in your refrigerator.

If the average basement temperature is below 18°C (65°F), the best type of dehumidifier to get is a desiccant model. But, if the average basement temperature is above 18°C (65°F), consider getting a refrigerant dehumidifier.

Determine if You Plan to Use Your Dehumidifier Year-Round

If you plan to use your dehumidifier year-round, simply choose a unit with enough power for your basement. If you are only using it during certain months of the year, consider purchasing a dehumidifier with an auto-defrost feature. This will ensure that the coils don’t freeze up during colder seasons.

Determine Your Usage

Some people want a dehumidifier for their basement and not their entire home. If this is your case, you might be wondering if it’s even worth purchasing a central unit. The answer to this question comes down to how often and for how long you plan on using your dehumidifier each year.

While cheap dehumidifiers will help keep your basement dry, they don’t have the power or features that mid-range or high-end units have. Remember, if your dehumidifier can’t keep up with the air in your basement, you’ll end up with water damage down the road.

So think about how often you plan on using it and then decide from there whether or not a whole-house dehumidifier will work for you.

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How Much Money Are You Willing to Spend?

After all, this is your home we’re talking about. You might not want to spend a ton of money on a dehumidifier, but remember, the last thing you want is for something in your basement to start rusting and decaying because you didn’t do enough research and ended up with an inferior unit.

The good news is that there are quality units on the market that won’t cost you an arm and a leg. It’s simply a matter of doing some research to find one at a price point you can afford.

Dehumidifier Sizing Chart

Dehumidifiers are sized according to the amount of water they can dehumidify in a given period. When sizing yours, you want to make sure you pick a model capable of removing enough humidity at a given time. But before that, you will need to know the most ideal dehumidifier capacity for your basement, depending on its room size and the dampness level. Once you have these two values, you can cross them to the AHAM Dehumidifier Sizing Chart below.

Humidity Levels (%) Size of the Area to be Dehumidified (sq. ft.)

300 sq. ft.500 sq. ft.800 sq. ft.1200 sq. ft.
Slightly Damp Air
Heavier Air & Musty Smell
Water Beads on Floor and Walls
Standing Water on the Floor

Related Questions:

How much humidity is too much for a basement?

As a general rule, any humidity level above 65 percent can be considered too much for a basement. Specifically, anything over 80 percent is dangerous and can lead to water stains and mold problems. Because of this, you’ll want to make sure that you use a dehumidifier with the proper capacity for your basement.

Why are basements a source of dampness in most homes?

There are several reasons why basements become more prone to dampness than other rooms of your home. Water might pene¬¬trate cracks in the foundation or walls, high humidity can be caused by different activities like laundry and bathing, and condensation on cool surfaces (like windows) can also lead to dampness.

About the author

Sharif Hasan

I am Sharif a data-driven marketer by profession and run The Spruce Air. I am very interested in keeping good-quality air inside of my home. Besides, I love to share my air-related knowledge through my website.

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