What Size Dehumidifier Do I Need? Pints by Dampness

By Ray Bennett · Updated 2 October 2026 · 4 min read · Checked against the sources at the end

What Size Dehumidifier Do I Need? Pints by Dampness

Short answer

ENERGY STAR sizes a portable dehumidifier by how damp the space is: 20 to 30 pints a day for a damp room under 2,000 square feet, 25 to 40 for a very damp one, and 30 to 50 where walls sweat or water seeps in. It says better to oversize than undersize. Ratings dropped in 2019 when DOE began testing at 65°F, so an old 50 pint model is roughly a new 30.

What size dehumidifier do I need? ENERGY STAR sizes them by two things: how big the space is, and how damp it is before you start. Its chart gives a range in pints a day for each, and it says it is better to oversize than undersize.

There is one trap in the numbers. The ratings changed in 2019, so a new model with a smaller pint figure may do the same job as an old, bigger one. This page covers both.

Before you start

What to carry: a humidity meter if you have one, a torch for the corners, and a tape measure. Fifteen minutes.

Gas or electric? Either. A dehumidifier runs on electricity, whatever heats the house.

Judge the damp. Look for a musty smell, damp spots on walls or the floor, and walls or floors that sweat. A humidity meter reading settles it.

What ENERGY STAR and EPA are clear about. Fix the water first. EPA says an air cleaner or filter does not fix mold: the cause is water or moisture, and the source has to be found. A dehumidifier dries the air, not a leak.

Cold basements. ENERGY STAR says frost can form on the coils below 65°F, making the compressor cycle without removing moisture. Switch it off and let it defrost.

A full bucket stops it. ENERGY STAR says most portable models shut off when the bucket is full. A unit that has stopped may simply need emptying.

The chart

ENERGY STAR's sizing chart for portable dehumidifiers, in pints a day under the current test.

Check 1

Match the damp to the pints

Damp. The space feels damp and smells musty now and then, at 50 to 75 percent humidity: 20 to 30 pints a day under 2,000 square feet, 30 or more above.

Very damp. It always feels and smells damp, with damp spots on walls and floors, at 75 to 90 percent: 25 to 40 pints, or 40 or more.

Wet. Walls or floors sweat or water seeps in, or laundry dries there, at 90 to 100 percent: 30 to 50 pints, or 50 or more.

Minimums, not targets. ENERGY STAR calls these the minimum capacity for the space, which is why it adds that bigger is the safer mistake.

Replacing one. ENERGY STAR says to judge by how much water you empty from the old one each day.

Why the pint numbers dropped

ENERGY STAR's rough guide from old ratings to new. The change for a given model varies, and the maker can compare them more closely.

Check 2

Compare old and new ratings properly

What changed. ENERGY STAR says DOE’s test since June 2019 runs portable dehumidifiers at 65°F instead of 80°F, closer to a basement. There is less water to remove in cooler air, so the ratings dropped.

The rough match. An old 30 pint model is roughly a new 20, an old 50 roughly a new 30, an old 70 roughly a new 40 to 45, and an old 90 roughly a new 55.

Whole home units. ENERGY STAR gives an old 80 as roughly a new 70, and an old 120 as roughly a new 100.

Choosing and running it

Check 3Free to check

Pick the features that fit the space

Efficiency. ENERGY STAR says efficiency is shown as the integrated energy factor, liters removed per kilowatt hour, and higher means more efficient.

Drainage. Most portable models use a bucket. Some take a hose to a floor drain or sump pump. A whole home unit drains to a floor drain or a condensate pump: a condensate pump not working.

Low temperatures. For a space that stays below 65°F, ENERGY STAR suggests a model rated for lower temperatures, or one with an anti frost sensor.

Whole home, or fix the cause

Check 4

Decide if a whole home unit makes sense

How they work. ENERGY STAR says whole home units usually use the house’s own air ducts to dry one or more rooms, and are often permanent.

When ENERGY STAR suggests one. In a humid climate, with central air, in a fairly well sealed house where the humidity stays above 55 percent throughout.

Sealing helps it. ENERGY STAR says home and duct sealing improve a whole home dehumidifier’s performance and cut its energy use.

Humid with the AC on. An air conditioner should take out humidity too. When it does not, the causes are here: a house that is too humid.

Questions people ask

What size dehumidifier do I need for a basement?

By ENERGY STAR’s chart, 20 to 30 pints a day for a damp one under 2,000 square feet, 25 to 40 if very damp, and 30 to 50 if the walls sweat or water seeps in. Oversize rather than undersize.

Is a 35 pint dehumidifier the same as a 50 pint?

Roughly, if the 35 is a new rating and the 50 an old one. ENERGY STAR matches an old 50 to about a new 30, and an old 60 to about a new 35.

Can a dehumidifier be too big?

ENERGY STAR says it is better to oversize than undersize a dehumidifier.

Why does my dehumidifier ice up in the basement?

ENERGY STAR says frost forms on the coils below about 65°F. Switch it off, let it defrost, and consider a model rated for low temperatures.

How do I know how damp my basement is?

ENERGY STAR’s chart counts 50 to 75 percent humidity as damp, 75 to 90 as very damp and 90 to 100 as wet. A cheap humidity meter tells you which one you have.

Will a dehumidifier fix mold?

Not on its own. EPA says mold comes from water or moisture, and the source has to be found and the mold cleaned up.

Sources: ENERGY STAR "Dehumidifiers" buying guidance and "Dehumidifier Testing and Capacity", and EPA's Guide to Air Cleaners in the Home (2018)