Correctly sizing a dehumidifier is the first thing you need to do.
The capacity of most residential dehumidifiers ranges from 30 pints to 70 pints.
What size dehumidifier do I need? Can a dehumidifier be too big?
Here’s the deal:
If you buy a dehumidifier that’s too big or one that’s too small, you will either be left with:
- Higher dehumidifier/electricity cost (too big).
- Humid home (too small).
When homeowners try to size a dehumidifier, we usually decide how big a dehumidifier we need based on what we need it for. In short, we incorrectly size a dehumidifier according to:
- If we need it for the basement. Basements have high relative humidity, 70% to 100%, and low square footage. Dehumidifiers are perfect for extracting that moisture.
- Suppose we need it for the whole house. Houses usually have 50% to 70% relative humidity and higher square footage.
What really matters when picking the correct size of a dehumidifier are 3 specific factors:
- Relative humidity rates. They range from 50% to 100%. The purpose of using a dehumidifier is to lower relative humidity to 30% to 50%.
- Square footage. A smaller area (under 500 sq ft) will obviously need a smaller capacity of the dehumidifier (30 or 50 pints) than a bigger 1000+ sq ft area.
- Average temperature. Temperature is the most overlooked factor when it comes to what size dehumidifier you need.
Most homeowners have a specific situation. Picking the correct size of a dehumidifier is not the simplest task in the world. However, we will help you get a rough estimate of how big a dehumidifier you need for your basement or house.
The most useful resource is the dehumidifier size chart. AHAM (Association of Home Appliance Manufacturers) has come up with directives on the capacity of dehumidifiers for different relative humidity and area sizes.
You can jump to the dehumidifier size chart here.
2 Dehumidifier Sizing Standards Currently In Use By Department Of Energy
One thing to be aware of before checking the sizing chart and using the calculator. As adopted by the Department of Energy (DOE), there are 2 testing standards for modern dehumidifiers:
- Old standard from 2012.
- New standard adopted in 2019.
If you looked at any dehumidifier – you can check the best dehumidifier currently on the market here, for example – you will see something like ‘Midea MAD50C1ZWS Dehumidifier New 50 Pint-2019 DOE (Previous 70 Pint)‘.
Why does a dehumidifier that had a capacity of 70 pints have a new capacity of 50 pints? The device is the same; what changed is the DOE sizing standard.
The old 2012 standard took into account Energy Factor. The new 2019 standard considers the Integrated Energy Factor that is more accurate in representing the capacity of a dehumidifier. The new 2019 testing procedure also tests dehumidifiers at a lower temperature (65°F) while the older standard test temperature was 80°F.
That’s why both the dehumidifier size chart and dehumidifier size calculator include both old and new capacity.
Here is a quick graphic representation of how old vs. new sizing standards differ. The example is made for a 500 sq ft area (room/basement/house):
Let’s look at the 75% relative humidity. According to the old standard, you would need a 50-pint dehumidifier. However, according to the new standard, you would need a 30-pint dehumidifier.
After 2023, only the new standard will be in use. Up until that time, both standards are in use.
Dehumidifier AHAM Size Chart
Let’s start with the capacity of the dehumidifier. You can get a small 30-pint, a medium 50-pint, or the strongest residential 70-pint dehumidifier. This tells you the maximum amount of water (in pints per day) a dehumidifier can squeeze out of your air per day, according to the tests made by DOE.
A pint is a weird unit; it amounts to 1/8 of a gallon. In short, the big 70-pint dehumidifier can absorb almost 9 gallons of water out of the house or basement air per day.
How big a dehumidifier should you buy?
Here is a quick look at the Association Of Home Appliance Manufacturers (AHAM for short) table. You need to know how many sq ft of space you have and how humid those spaces are:
AHAM Dehumidifier Capacity Table
| Humidity Levels: | 300 sq ft space | 500 sq ft space | 800 sq ft space | 1,200 sq ft space |
|---|---|---|---|---|
| 50-60% Humidity (Air feels slightly heavy) | 30 Pint (Old Standard) 20 Pint (New Standard) | 45 Pint (Old Standard) 30 Pint (New Standard) | 60 Pint (Old Standard) 40 Pint (New Standard) | 70 Pint (Old Standard) 50 Pint (New Standard) |
| 60-70% Humidity (Occasional musty smell) | 30 Pint (Old Standard) 20 Pint (New Standard) | 45 Pint (Old Standard) 30 Pint (New Standard) | 60 Pint (Old Standard) 40 Pint (New Standard) | 70 Pint (Old Standard) 50 Pint (New Standard) |
| 70-80% Humidity (Wet spots on walls or floor) | 40 Pint (Old Standard) 25 Pint (New Standard) | 50 Pint (Old Standard) 30 Pint (New Standard) | 65 Pint (Old Standard) 45 Pint (New Standard) | 80 Pint (Old Standard) 55 Pint (New Standard) |
| 80-100% Humidity (Seepage on walls, mold possible) | 45 Pint (Old Standard) 30 Pint (New Standard) | 60 Pint (Old Standard) 40 Pint (New Standard) | 70 Pint (Old Standard) 50 Pint (New Standard) | 90 Pint (Old Standard) 60 Pint (New Standard) |
For example, if you have a 500 sq ft basement with medium humidity (70%-80%), you would need a 50-pint dehumidifier. That’s a ballpark figure.
Note that some producers might be throwing around numbers like 3,000 sq ft or 4,500 sq ft. Long story short, it’s best to ignore those ‘calculations’. Here’s the real-life advice:
Always buy a big bigger dehumidifier. 70-pint ones are perfect for a majority of houses or basements.
Let’s look at 2 practical cases to get a grip on how to size a dehumidifier.
Example 1: 500 Sq Ft Basement With Very High Relative Humidity (80%)
Dehumidifiers are the most useful for very moist basements. Basements generally have an above-average humidity; this can spur spore and mold growth. In several decades, it can weaken the walls and put the whole structure of the house in danger.
Installing a dehumidifier makes a whole lot of sense. Here are the basic metrics of the basement (as an example):
- Square footage: 500 sq ft.
- Relative humidity: 80%.
- Average temperature: 70°F.
If we check the dehumidifier sizing table above, we can see that the basement with these specs would need a 50- or 60-pint dehumidifier (according to the old standard) or a 25-30 pint one (according to the new standard).
Whenever you have this kind of choice between a smaller (50-pint) and bigger (60-pint) dehumidifier, always use the higher capacity. It’s always better to have a more powerful dehumidifier than one that’s too weak to do the job.
Do keep in mind that AHAM sizing chart doesn’t take the average temperature into account. If you have a cold basement, it makes sense to add 10 pints to the overall size of the dehumidifier.
Dehumidifiers have to work extra hard in colder environments.
Example 2: 1200 Sq Ft House With 65% Relative Humidity
One dehumidifier can be enough to lower the relative humidity in a small house. Compared to basements, the whole house has higher square footage but lower relative humidity.
That means a dehumidifier has to extract moisture from a larger volume of air. However, the amount of moisture in the air is overall lower.
Here are basic metrics for a small house (as an example):
- Square footage: 1200 sq ft.
- Relative humidity: 65%.
- Average temperature: 70°F.
Checking the sizing table, we can deduce that such a house would need a 70-pint dehumidifier (old standard) or 50-pint one (new standard). For bigger spaces, you might want to look into the high-capacity commercial dehumidifiers.
I live in a up stairs apartment.The size is 65’by65’. It gets very warm in the summer. What size dehumidifier should I get.
Hello James, the high temperature goes hand in hand with high humidity. Luckily, at higher temperatures, dehumidifiers are much more effective at removing air moisture than at lower temperatures. They 65′ by 65′ are inches? So about 5-6 feet by 5-6 feet? For that, you will need a very small 20 Pint unit. If those are feet, you will need a big one, at least 50 Pint unit. For bigger units, you can check the whole house dehumidifiers here. For smaller areas, these quiet dehumidifiers are the best.
I bought innovative dehumider inwall with drain hookup an the company states it can handle 1500 sq ft basement well my basement is 650 sq ft I set the humidty level at 35% running 1 week 24/7 an it only gets to 53%. The unit is rated at 25 pts. If you have any size basement do not et a dehumidfer any lower then 50 pts
35% indoor humidity is really low, air that dry can cause nose bleeds.
Interested in why your goal is to have the humidity so low?
Hello Jon, CDC recommends an indoor relative humidity level between 30% and 60%. Many people who are looking to buy a dehumidifier, are trying to protect against mold and mold infestation. Higher humidity rates are exponentially connected with the likelihood of mold infectation. The best way to protect against mold is by lowering the indoor relative humidity levels.
Hi there, We stay in a 2 story apartment on the 1st and 2nd levels. we have thick carpets throughout the house other than the bathrooms, tv room and kitchen. the total size of our unit is probably around 160m2. we struggle very much with moisture on doors, windows and walls with the musty smell upstairs. I have also noticed dark green spots appearing along the windows where the moisture collects. I know this is not safe at all and I would like to know which dehumidifier would be best suited for our unit.
Hello Aimee, what you are describing are the negative effects of high indoor humidity levels (60% or more). For that high humidity, you would need a bigger dehumidifier. The best-suited units would be the big 50 Pint (70 Pint according to old 2012 DOE standard) units, they are also referred to as non-ducted whole-house dehumidifiers; you can check these big whole-house dehumidifiers here.
We have a 1400 square ft condo in a location with an average humidity of 75 and up. Our a/c unit is set at 75 degrees, 50% humidity all year. What would you recommend to help reduce our a/c costs?
Hello Pat, those humidity levels are quite high. One way to reduce the AC costs would be to get a dehumidifier to carry part of the load AC is supposed to carry; however, dehumidifiers also run on electricity. In places with high humidity, it makes sense to use a dehumidifier. That’s how you enable an air conditioner to do its primary job: cool the air.
I am using a garage with 625 sq. ft. floor space and 13 ft. ceilings for car detailing, including washing. Although there’s a catch basin for wash water, the cement floor is frequently wet and the humidity very high, with condensation on window panes, walls, etc. Since we are located in upstate NY, this is particularly problematic from late fall through early spring when doors and windows must be kept shut. The indoor temperature is probably in the low 60’s during most of the cool/cold months —perhaps in the upper 50’s at night. The humidity invades the small attached office (150 sq. ft. with 6 ft. drop ceiling) since the door separating it from the car bays is often ajar and the windows there become covered with condensation.
Although this forum of questions/comments and replies refers to house-related issues, could you give me any recommendations on the specs I should aim for when choosing a dehumidifier for the car detailing area of my building and whether I should have a separate one for the office ?
Hello Richard, it’s apparent from your description of the situation that you have to reduce the humidity in your garage. Given the size of the garage (625 sq ft and 13 ft very high ceilings), you would need the biggest portable dehumidifier for the garage. Those are the old 70 pint units (today’s 50 pint units). They usually have a specified coverage of up to 4,500 sq ft but you have to take that with a BIG grain of salt. For some specific suggestions, you can check our list of the best dehumidifiers for the basement. The basement and garage are pretty comparable environments as far as moisture levels are concerned.
By decreasing the relative humidity levels in the garage, you should also see a reduction in humidity in the attached 150 sq ft office. Hope this helps.
I have a crawl space that is approximately 10,000 cu ft and I am deciding between two dehumidifiers. The humidity level is relatively high ( I live in humid South Carolina but there is no mold present or standing water and the space is moderately sealed).
Below are the primary differences that I am concerned with:
AprilAire E80 Aprilaire E100
Capacity 65ppd @73 deg 60%RH 85ppd @73 deg 60%RH
Energy Factor 2.35/kw-h 2.35/kw-h
Airflow 185CFM 280CFM (BIG DIFFERENCE HERE)
Power Draw 5.1 Amps 6.9 Amps (BIG DIFFERENCE HERE)
Sq Ftg 4400 sq ft max 5500 sq ft max
The units are not that far apart in price so the above factors will determine my decision. Here’s my quandary, the E80 seems to be sized about right for my space but I am concerned with mainly the significantly lower airflow while balancing the lower power draw.
Is 185 cfm adequate or will it struggle to turn over and dehumidify all the air and run more thus negating the power savings? Or will the E100 turn over and dehumidify the air quicker and run less thus balancing out the extra power draw?
I’m probably overthinking it but it’s a significant investment for the unit and for protecting the house so your input would be greatly appreciated!
Thanks,
Bryan Timmerman
706-373-5440
Hello Bryan, thank you for describing the situation in great detail. Correct me if I’m wrong with the specific selection of units; we are basically talking about this Aprilaire E80 vs this Aprilaire E100, right?
You are looking at this situation correctly; the primary concern is always size (capacity) but the secondary concern, especially with crawl spaces, should always be adequate airflow.
Comparing E80 vs E100, both will be adequately sized for a 10,000 cu ft, E100 might be a bit too big. However, as you have neatly pointed out, the difference in airflow is big; 185 CFM vs 280 CFM. Given the price difference is rather small, the E100 is a better choice. You will need quite a lot of airflow and E80, albeit being adequately sized as far as dehumidification rate, might just be enough (it’s under 200 CFM airflow for a crawl room).
The difference is amps isn’t important; it’s just the power input and the bigger E100 draws more amps than the smaller E80. Considering these differences, the Aprilaire E100 is the best choice here. Hope this helps.
I have a fitness center with an aerobic floor that expands and contracts with temperature changes. With an increase in heat/humidity, my floor is bubbling up. My room square footage is around 1,700 sq feet. What size dehumidifier and pint size do you recommend I use to reduce the level of humidity so the floor doesn’t bubble up? Thanks for your time.
Hello Stacie, that sounds quite scary. The size depends on your humidity levels. In any case, with such a big place, you should look into ducted whole-house dehumidifiers. Something in the range from 60 Pint/day to 90 Pint/day would be presumably sufficient. If you need a more practical recommendation, you can check some good whole house ducted dehumidifiers and their sizes here.
I have a ranch style house with 2030 sq. ft. on the ground floor. Underneath I have a 1373 sq. ft. basement and 657 sq. ft. crawl which opens into the basement. I have HVAC duct in the basement to provide air flow and the humidity in the basement sometimes gets above 70%. I have a 35 pint in the basement that will get the level down to 62% on bad days. I’ve noticed that the humidity upstairs goes down when I’m running the dehumidifier in the basement – I’m assuming because I’m circulating basement air upstairs by the air conditioning. I’m considering purchasing another dehumidifier with a Energy Star rating to knock down the utility costs. On this new model should I consider the square footage of the basement, crawl space and living areas? Everything I find online only considers the basement and crawl space.
Hello Paul, if you have an existing 35-pint dehumidifier and feel that the humidity levels are fine, you should just replace it with a 35-pint Energy Star rated unit. If you need a little higher dehumidification rate, the next size is a 50-pint one. Hope this helps a bit.
Hi
I have a 3500 sq foot home. Basement is damp using a 40 pint dehumidifier what size should I move up to? My dehumidifier is old and needs to be replaced not doing a good job. My laundry ends in the basement and the clothes are damp e feeling. I am confused by the research information.
Thank you. Ann
Hello Ann, the best thing here would be to opt for the biggest stand-alone dehumidifier. Currently, that is a 50-pint dehumidifier, according to the new ratings. You can check these dehumidifiers for the basement; note that they still have the old 70-pint capacity in the specs. These are older specs; all of these 70-pint units are actually the big 50-pint units, according to the new rating. Hope this helps.
My basement is 832 sq ft
The humidity runs 75-85%
I have been trying to kill the mold out and hopefully get rid of the smell.
What size dehumidifier do I need
Thank You
Hello Steven, you should aim for about 60% humidity levels in the basement; below 50% would be perfect. For a big 832 sq ft basement, the 50-pint dehumidifier would be best (new 2019 capacity rules, that is 70-pint according to the old 2012 DOE rules). You can check these dehumidifiers for basement, aim for that 70-pint capacity. That should reduce the moisture levels below 60%.
Thanks for help. We have a 2 story house on slab. Only 1/3 of the downstairs slab area smells musty. So this open area of 750 ft. doesn’t smell musty everywhere, just the third facing the west. Mostly on days where temp. is from 83 to 100 degrees in the summer. What size would you use in that area?
Hi David, high temperature is correlated with high humidity. The third facing west will usually receive the most sunlight when we are home (afternoon hours), thus the higher temperature – higher localized humidity levels – musty smell. Since it’s not that big an area, the 30 pint humidifier or 35 pint humidifier (new 2019 DOE capacity) should do the trick. Hope this helps.
I jabe a 38ft boat that is docked in a marina I want to make sure I get the right size dehumidifier
Hi David, boat dehumidifiers are another story. We just don’t have enough understanding of the effect of the sea on increasing humidity levels, and we can’t make an adequate recommendation here. Sorry.