What Size Dehumidifier Do I Need? Pints Per Day Chart

A dehumidifier's size is its capacity: the pints of water it removes from the air in 24 hours. A 1,000 ft² basement that only feels damp in humid weather needs about 14 pints a day on the older rating, or about 10 on the current label. A wetter space needs more. To pick the right one, you need the floor area and an honest read of how damp the space is.

Step 1: Judge how damp the space is

• Moderately damp: the space feels damp and smells musty only in humid weather.
• Very damp: it smells musty all the time, and there are damp spots on the walls or floor.
• Wet: the walls sweat, the floor is damp, or water seeps in after rain.
• Extremely wet: there is standing water, a leak or flooding. A dehumidifier is not the fix for water coming in: stop the water first.

Step 2: Read the chart

The long-standing sizing chart (Energy Star and the appliance industry) gives pints per day by floor area and dampness. It was set at 80°F and 60% humidity, and numbers on older boxes and listings use it. For 8 ft ceilings:

The 2019 rating change

In 2019 the US Department of Energy changed the test conditions to a cooler 65°F, which is closer to a real basement. The same machine is now rated about 30% fewer pints than before: a unit once sold as 50 pints is now a 35-pint model. Newer labels and listings use the current rating, so multiply the old figure by about 0.7 to compare:

Check which rating a product uses, and compare with the same column. The dehumidifier size calculator shows both and rounds up for you.

Adjust for your space

• Ceiling height. The chart assumes 8 ft ceilings. A 10 ft ceiling has 25% more air to treat, so scale the result up by about a quarter.
• Extra moisture. Add about 5 pints if the space has a laundry, you dry clothes indoors, or it often holds a crowd of people.
• Odd spaces. A big open basement dehumidifies more slowly than closed rooms. Doors that stay open let moisture in from the rest of the house.
• If you are between sizes, buy the larger one. It reaches the target sooner and then rests, while an undersized unit runs all day and never gets there.

What to aim for, and how to place it

Keep indoor humidity between 30% and 50%, and below 60% at all times. Mold and dust mites thrive above that. A hygrometer costs a few dollars and tells you what the room is doing. Put the unit in the middle of the space with a few feet of clearance on every side, away from walls and furniture, so it can pull air through. Use a hose to a floor drain, or a model with a built-in pump, so that you are not emptying the bucket every few hours.

What it costs to run

A 35-pint dehumidifier draws roughly 450 W while the compressor runs. Running 12 hours a day for 30 days at 17 cents per kWh is 162 kWh, or $27.54 a month. Use the appliance electricity cost calculator with the watts on your unit's label, and check the Energy Star rating, which tells you liters of water removed per kWh. A more efficient model costs less to run for the same job.

Fix the source too

• Point downspouts and the ground away from the foundation, so that rain does not run toward it.
• Seal cracks in basement walls and floors, and use a vapor barrier in a crawl space.
• Vent the clothes dryer, bathroom fans and range hood outdoors.
• Below about 60°F, a compressor dehumidifier ices up and works poorly. A cold basement needs a unit rated for low temperatures.