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What size dehumidifier do I need?

By Nazrul Islam. Updated October 11, 2026.

What size dehumidifier do I need for my room?

Dehumidifiers are sized in pints of water removed per 24 hours. Pick the size from two things: how big the space is and how damp it feels before you start. ENERGY STAR publishes this chart.

ENERGY STAR says it is better to oversize than undersize. A larger unit reaches your target faster and cycles off more. An undersized unit may run nonstop and never get there.

You can judge dampness by feel and by clues. Musty smells, damp spots on walls, and condensation on cold pipes suggest “very damp.” Standing water or wet floors mean “wet.” A cheap hygrometer gives you an actual number.

If you are replacing an old unit, ENERGY STAR notes you can also size from how much water you empty each day. Just keep the rating change below in mind.

Why did dehumidifier pint ratings change?

Units made on or after June 13, 2019 are rated under the Department of Energy test in 10 CFR 430, Appendix X1. That test runs portable units at 65°F and 60% relative humidity. Older ratings were measured at 80°F and 60% RH.

Cooler air holds less water, so the same machine pulls out less per day at 65°F. The labels dropped even though the hardware did not shrink. TCL’s published conversion shows the pattern:

So an old “70-pint” basement unit is about a new “50-pint” unit. Whynter lists its RPD-506EWP the same way: 50 pints under the 2019 standard, 70 pints under the older one. Treat this table as an approximation. Conversions vary by brand and model.

When shopping, compare only new ratings against each other.

What humidity should a dehumidifier be set to?

The EPA recommends keeping indoor humidity below 60%, ideally between 30% and 50%. ENERGY STAR gives the same 30-50% range and notes higher levels may promote mold.

In practice, set the built-in humidistat to about 45-50% for a basement in summer. Going much lower costs more electricity and gains little. In winter, homes usually need less drying, not more. See our guide to ideal indoor humidity in winter for cold-weather targets.

How much does it cost to run a dehumidifier?

Here are rated power figures from manufacturer spec sheets:

Rated power is close to the maximum draw while the compressor runs. Actual average use is lower, because the unit cycles off once it hits the set humidity.

Cost per hour = watts / 1,000 x price per kWh. For a 600 W unit at 18¢: 0.6 kW x $0.18 = $0.108 per hour.

The monthly columns assume 12 hours of compressor run time per day for 30 days (216 kWh and 324 kWh). That is an example, not a measurement. A sealed, mildly damp basement may need far less. EIA expects the 2026 U.S. average residential price at about 18.2¢ per kWh, so the 18¢ row is a fair middle case.

What does the L/kWh efficiency rating mean?

Efficiency is the integrated energy factor (IEF), in liters of water removed per kWh. Higher is better. ENERGY STAR certified models use about 20% less energy than comparable conventional units.

You can turn IEF into energy per day. One pint is 0.473 liters, so 50 pints is 23.7 liters.

• Energy per day = liters removed / IEF
• 50-pint unit at full capacity, IEF 1.8: 23.7 / 1.8 ≈ 13.1 kWh, or about $2.37 at 18¢
• 35-pint unit at full capacity, IEF 1.6: 16.6 / 1.6 ≈ 10.35 kWh

Spec-sheet watts and IEF come from different test conditions, so these figures won’t match the wattage math above exactly.

Canada’s minimum efficiency rules use the same DOE test method. Natural Resources Canada lists these minimums:

Whole-home units have minimums of 1.77 L/kWh (case volume 8 cubic feet or less) and 2.41 L/kWh (larger).

Note that a 50-pint unit has a lower minimum than a 51-pint unit. Check the actual IEF on the spec sheet or ENERGY STAR listing, not just the size.

What size dehumidifier for a basement or crawl space?

Basements are often “very damp” in summer, so many land in the 30-50 pint range. A finished basement over 2,000 sq ft, or one with past water problems, points to 50 pints or a whole-home unit.

Fix water sources first. ENERGY STAR recommends:

• Extending downspouts away from the foundation and keeping gutters clear
• Sloping soil away from the house
• Not overwatering foundation plantings
• Venting the clothes dryer outdoors and using bath and kitchen fans
• Repairing leaking outdoor faucets

Crawl spaces are a special case. Portable units are not built for dirt floors, tight access, or dripping into a bucket nobody checks. Many crawl spaces need moisture fixes, a vapor barrier, or a dedicated unit installed by a contractor. Get the moisture source diagnosed before buying.

Will a dehumidifier work in a cold basement?

Below about 65°F, frost can form on the coils, according to ENERGY STAR. The compressor may then cycle without removing water. If you see frost, turn the unit off and let it thaw.

Many current models handle this with auto-defrost or anti-frost sensors. Check the operating range on the spec sheet. The Friedrich units above list 41°F to 90°F. The Whynter lists a 40°F minimum with auto-defrost. Below those limits, a compressor dehumidifier is the wrong tool.

How do dehumidifiers drain?

A 50-pint unit can fill a 13-16 pint bucket several times a day in wet conditions. In a basement, a hose or pump is usually worth it.

Dehumidifier safety tips

• Plug directly into a wall outlet. Avoid extension cords and power strips for a compressor appliance.
• In basements and other damp areas, a GFCI-protected outlet is a sensible precaution.
• Keep the unit on a level surface with clear space for airflow.
• Clean the filter regularly and empty or rinse the bucket to prevent mold.
• Route hoses so they cannot kink or spill near electrical equipment.

Quick answers

What size dehumidifier do I need for a 1,500 sq ft basement? ENERGY STAR suggests 25-40 pints if it is very damp and 30-50 pints if wet. Many people choose a 35- or 50-pint unit and lean larger.

Is a 35-pint dehumidifier enough? For a slightly to very damp space under 2,000 sq ft, usually yes. For wet basements or larger areas, a 50-pint unit is the safer pick.

Is a new 50-pint dehumidifier the same as an old 70-pint? Roughly, yes. Ratings since 2019 are tested at 65°F instead of 80°F, which lowers the label without changing the hardware.

What humidity should I set my dehumidifier to, and does it work in a cold basement? Keep humidity below 60%, ideally 30-50%, per the EPA; around 45-50% suits most basements. Below about 65°F coils can frost, so choose a unit with auto-defrost and check its minimum operating temperature, often around 40°F.

How much does a 50-pint dehumidifier cost to run? At 900 W and 18¢ per kWh, about 16¢ per running hour. At 12 hours a day, that is about $58 a month.