Plug Count

What Size Dehumidifier Do I Need? Basement and Crawl Space Sizing

Heating & coolingUpdated 8 min readBy the Plug Count editorial team
A portable dehumidifier running on the concrete floor of an unfinished basement, with a drain hose leading to a floor drain.

What size dehumidifier you need depends on how damp the space is and how big it is. ENERGY STAR's chart puts a moderately damp room under 2,000 sq ft at 20–30 pints a day, a very damp one at 25–40 pints and a wet basement at 30–50 pints. Larger spaces need more, and ENERGY STAR says oversizing beats undersizing.

Key facts

  • ENERGY STAR sizes dehumidifiers by pints of water removed per day, based on dampness and floor area (under or over 2,000 sq ft).
  • The DOE test changed in 2019 (portable units now tested at 65°F instead of 80°F), so new pint ratings look smaller: an old 70-pint unit is roughly a new 40–45-pint unit.
  • EPA advises keeping indoor humidity below 60%, ideally 30–50%.
  • A typical portable dehumidifier draws about 400 W while running; ENERGY STAR models use about 20% less energy than conventional ones.
  • The International Residential Code accepts dehumidification, sized to the manufacturer's specifications, as one way to handle an unvented crawl space.

Dehumidifier size chart: how many pints do I need?

ENERGY STAR's current consumer chart groups spaces by how damp they are before you start dehumidifying, then by size. Capacity is pints of water removed per 24 hours.

Condition (without a dehumidifier)Room or area under 2,000 sq ftOver 2,000 sq ft
Slightly to moderately damp (about 50–75% RH)20–30 pints30+ pints
Very damp: damp spots on walls or floors (about 75–90% RH)25–40 pints40+ pints
Wet: sweating walls or floors, seepage, or laundry drying (about 90–100% RH)30–50 pints50+ pints

Two practical shortcuts from ENERGY STAR:

  • When in doubt, go bigger. A larger unit reaches your target humidity sooner and then cycles off; an undersized one runs nonstop and may never catch up.
  • Replacing an old unit? Look at how much water you empty from the bucket each day. That is a real-world measure of the moisture load.

Our dehumidifier size calculator runs the same chart for your space.

Why do new dehumidifiers have smaller pint ratings?

In June 2019 new federal standards and test rules took effect. Portable dehumidifiers used to be rated at 80°F; they are now tested at 65°F, which is closer to real basement conditions. Cooler air holds less moisture, so the same machine removes fewer pints in the test. Ratings based on the new test started showing up on boxes in early 2020.

That matters when you compare an old unit (or an old article) with what is on sale now. ENERGY STAR publishes this approximate equivalence; actual figures vary by model, and the manufacturer is the best source for a specific unit.

TypeOld rating (through 2019)Approximate new rating (2020 on)
Portable30 pints20 pints
Portable40 pints25 pints
Portable50 pints30 pints
Portable55 pints30–35 pints
Portable60 pints35 pints
Portable70 pints40–45 pints
Portable90 pints55 pints
Whole-home80 pints70 pints
Whole-home100 pints85 pints
Whole-home120 pints100 pints
Whole-home140 pints115 pints
Whole-home160 pints135 pints
Whole-home200 pints170 pints

So a "50 pint dehumidifier" sold today is a much larger machine than a 50-pint unit from 2015, which would be rated about 30 pints now.

The older square-foot chart (pre-2019 pints)

Many sites still print a chart by square footage. It comes from the Association of Home Appliance Manufacturers and once appeared on ENERGY STAR's "Dehumidifier Basics" page. Its numbers are old-test pints, so don't use them to pick a unit rated under today's test without converting.

AreaModerately dampVery dampWetExtremely wet
500 sq ft10121416
1,000 sq ft14172023
1,500 sq ft18222630
2,000 sq ft22273237
2,500 sq ft26323844

Legacy AHAM chart, pints per day under the pre-2019 test. We found no official per-square-foot chart for current ratings; use the ENERGY STAR range chart above instead.

What size dehumidifier for a basement?

Basements are the most common reason people buy a dehumidifier, and they are usually the dampest part of the house. Start by judging the condition honestly:

  • Musty smell only in humid weather: moderately damp, so 20–30 pints for a basement under 2,000 sq ft.
  • Constant musty smell, damp patches on walls or floor: very damp, 25–40 pints.
  • Sweating walls, seepage, or clothes dried indoors: wet, 30–50 pints.

Two basement details change the choice:

  • Temperature. Below about 65°F, frost can build up on the coils and the unit cycles without removing much water. ENERGY STAR suggests a model rated for lower temperatures if your basement is often that cool; units with an anti-frost sensor shut off to defrost on their own.
  • Drainage. Emptying a bucket every day gets old fast. Many portable units accept a hose to a floor drain or sump pump, and some have a built-in pump. Keep hoses and water away from cords and outlets.

Also cut the moisture at its source. ENERGY STAR points to clear gutters, downspouts that discharge away from the foundation, soil sloped away from the house, and not overwatering foundation plantings. A dehumidifier treats the air; it won't stop water coming through a wall.

Do you need a crawl space dehumidifier?

It depends on how the crawl space is built. Traditional crawl spaces are vented to the outdoors. Many newer or retrofitted ones are sealed ("unvented" or "encapsulated"), and those need some way to control moisture.

  • What the code allows. The International Residential Code's section on unvented crawl spaces (R408.3, as adopted by states and counties) requires a continuous vapor retarder over exposed earth, with joints overlapped 6 inches and sealed and edges run at least 6 inches up the stem wall. It then lists ways to condition the space, and one of them is dehumidification sized to the manufacturer's specifications. The others are a small exhaust fan, a conditioned-air supply, or a plenum in qualifying existing homes. Local amendments vary, so check with your building department.
  • Why humidity control matters there. In a Department of Energy Building America study of two sealed crawl spaces in Ithaca, New York, relative humidity in the crawl spaces stayed above 60% from April through November. The same study found sealed crawl spaces cut space-conditioning energy use by 15–18% compared with vented ones. It was a small, cold-climate study, so treat it as a sign of the problem, not a rule for every home.

Size a crawl space unit to the manufacturer's coverage figures for that model, and have a contractor who does crawl space work confirm the vapor barrier, drainage and any standing-water issues first. Crawl spaces are hard to reach, so a unit that drains continuously (gravity drain or condensate pump) is the practical choice.

What should a dehumidifier be set to?

EPA recommends keeping indoor relative humidity below 60%, ideally between 30% and 50%, to limit mold growth. ENERGY STAR gives the same 30–50% range and suggests 30–40% in cold climates during the heating season to avoid condensation on windows.

For most basements, a setting around 50% is a reasonable start. Setting it lower makes the unit run longer and use more electricity. If the dehumidifier has no humidity readout, an inexpensive hygrometer will show what is really happening. After a leak or flood, EPA says to dry wet materials within 24–48 hours to prevent mold.

How much electricity does a dehumidifier use?

A typical portable dehumidifier draws about 400 W while the compressor runs. Manufacturer spec sheets in our data show about 235 W for a 22-pint model, 380 W for 35 pints and 515 W for 50 pints. The compressor needs a short surge to start, about 800 W in Honda's chart. Details are on the dehumidifier watts page.

Efficiency is rated as the Integrated Energy Factor (IEF): liters of water removed per kWh. You can estimate average draw from the rating:

Average watts ≈ pints per day × 0.473 L per pint ÷ IEF ÷ 24 hours × 1,000

Capacity (new rating)ENERGY STAR v5 minimum IEFkWh to remove a full day's rated waterAverage watts
20 pints1.57 L/kWhAbout 6.0About 250 W
35 pints1.80 L/kWhAbout 9.2About 380 W
50 pints1.80 L/kWhAbout 13.1About 550 W

These are worst-case figures: the unit running all day at rated conditions. Once a space is dry, the compressor cycles. At about 400 W running 40% of the day, a mid-size unit uses around 3.8 kWh a day. At the 2024 US average of 16.48¢ per kWh (EIA), that is about 63 cents a day, or roughly $19 over 30 days. Check your state on the electricity rates page and plug in your numbers with the electricity cost calculator.

Running a dehumidifier during an outage

A dehumidifier is a low priority in most outages, but it can matter after a flood. A small inverter generator or a power station with about 1,000 W of surge capacity can start a typical unit; see what size generator do I need or estimate battery time with the runtime calculator. Keep any generator outdoors and well away from basement windows and vents.

Questions people ask

What size dehumidifier do I need for a basement?

For a basement under 2,000 sq ft, ENERGY STAR suggests 20–30 pints if it is moderately damp, 25–40 pints if very damp and 30–50 pints if wet. Go up a size if you are unsure.

What size dehumidifier for 1,000 or 1,500 square feet?

Both fall in ENERGY STAR's under-2,000 sq ft column, so dampness decides it: 20–30 pints for moderately damp up to 30–50 pints for wet. Older square-foot charts use pre-2019 pint ratings and run higher.

Is a 50 pint dehumidifier too big?

Rarely. ENERGY STAR says it is better to oversize than undersize, and 50 pints is the top of the range for a wet space under 2,000 sq ft. A bigger unit simply reaches the set humidity sooner and cycles off.

What should a dehumidifier be set on in a basement?

Aim for 30–50% relative humidity and keep it below 60%, per EPA. Around 50% is a practical setting for most basements.

Do dehumidifiers use a lot of electricity?

A typical unit draws about 400 W while running and uses roughly 3.8 kWh a day if it runs 40% of the time. ENERGY STAR models use about 20% less energy than conventional ones.

What size crawl space dehumidifier do I need?

The building code says to size crawl space dehumidification to the manufacturer's specifications, so use the coverage figure for the specific model. Seal the vapor barrier and fix any water intrusion first.

Sources

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