Maintenance procedure · Written to ASD-STE100 Issue 9 · Formatted to ANSI Z535

Choosing a Dehumidifier Capacity for a Room

Using room size and dampness to find a pint rating, and why a 2019 change in the government test means an old rating and a current rating are not the same number
ApplicabilitySelecting a portable dehumidifier for a single enclosed room or basement, or deciding whether a whole-home dehumidifier is worth pursuing with a professional. Not for sizing the duct connections or the installation of a whole-home system, and not for a room with an open floor plan or an unusual shape.
Task time12 min editorial estimate, not a measurement
PersonnelOne
Revisionv1 · 2026-08-04
BEFORE YOU BEGIN

Before you begin. This procedure is general reference information, not professional advice. Equipment varies by manufacturer, model, and year. Always follow the documentation supplied with your equipment — where it differs from this page, follow the manufacturer. Verify that you have the tools, the working conditions, and the ability to do this task safely. If anything is unclear, if the equipment is damaged, or if the task exceeds your experience, stop and use a qualified professional. You are responsible for your own safety and for the outcome. This site accepts no liability for any loss, damage, or injury arising from the use of this information.

Specifications marked unverified could not be traced to a manufacturer source. Do not rely on them — obtain the value from your equipment documentation.

Summary

Every dehumidifier carries a pint-per-day number, and matching that number to your room takes two facts: the room's floor area and how damp the room is without a dehumidifier running. ENERGY STAR publishes a chart that crosses two room-size groups with three dampness levels to give a recommended pint range. This page walks through measuring the room, judging its condition, and reading that chart, then helps you decide between a portable unit and a whole-home, duct-connected system.

The trap is the number itself. The U.S. Department of Energy changed the official capacity test in 2019, from 80-degree air to 65-degree air, so a pint rating from 2019 or earlier and a pint rating from 2020 or later are not the same measurement, even printed on an identical-looking box. This page gives ENERGY STAR's own old-to-new correlation table so a rating from either side of that change can be read correctly, and says plainly where it stops: an odd-shaped room, an open floor plan, or a whole-home duct system needs a professional, not this chart.

Necessary equipment

ItemNote
Tape measureMeasure the length and the width of the room in feet.
Pencil and paperRecord your measurements, your room's condition, and the chart range.
Rating plate or product listing for the dehumidifier optionalThe rating plate or the product page names the pint number and the date, if the source names a date.

Find the test year behind your rating

Estimated 5 min

NOTEA rating from before 2020 does not match a rating from 2020 or later.
NOTICE

DO NOT COMPARE A DEHUMIDIFIER RATING FROM BEFORE 2020 TO A RATING FROM 2020 OR LATER.
The government changed the test in 2019. The wrong comparison hides the correct size.

  1. Find the pint-per-day number on the dehumidifier or on the chart you plan to use.
    <1m
  2. Find the date of that number, if the source names one.
    <1m
  3. Treat a rating from 2019 or earlier as a different measurement from a rating for 2020 or later.
    • The U.S. Department of Energy changed the dehumidifier capacity test in 2019.
    • The new test uses the air at 65 degrees F.
    • The old test used air at 80 degrees F.
    • Cool air holds less moisture than warm air.
    • The same dehumidifier gives a lower number under the new test.
    • A lower number after 2019 does not mean a smaller or a weaker machine.
    2m
  4. Convert an old rating to an approximate new rating with this table, if you compare the two.
    • A 30-pint rating from 2019 or earlier is about 20 pints under the new test.
    • A 40-pint rating from 2019 or earlier is about 25 pints under the new test.
    • A 50-pint rating from 2019 or earlier is about 30 pints under the new test.
    • A 55-pint rating from 2019 or earlier is about 30 to 35 pints under the new test.
    • A 60-pint rating from 2019 or earlier is about 35 pints under the new test.
    • A 70-pint rating from 2019 or earlier is about 40 to 45 pints under the new test.
    • A 90-pint rating from 2019 or earlier is about 55 pints under the new test.
    • ENERGY STAR states that the actual change varies by model.
    2m
  5. Judge a replacement by the water you empty each day, if you replace an old dehumidifier.
    • ENERGY STAR gives this method instead of a direct comparison of the old number and the new number.
    <1m

Measure the room

Estimated 2 min

NOTEThe chart in this page sorts rooms into two sizes.
  1. Measure the length of the room in feet from wall to wall.
    <1m
  2. Measure the width of the room in feet from wall to wall.
    <1m
  3. Multiply the length and the width to find the area in square feet.
    • A room 12 feet long and 15 feet wide has an area of 12 x 15 = 180 square feet.
    <1m

Judge the room without a dehumidifier running

Estimated 2 min

NOTEPick the description that matches the room now.
  1. Judge the room by how it feels and smells without a dehumidifier running.
    • Slightly to moderately damp: the room smells musty at times.
    • Slightly to moderately damp is 50 to 75 percent relative humidity.
    • Very damp: the room always feels and smells damp. Wet patches show on the walls or the floor.
    • Very damp is 75 to 90 percent relative humidity.
    • Wet: water forms on the walls or the floor.
    • Wet is 90 to 100 percent relative humidity.
    2m

Find the capacity range for your room

Estimated 2 min

NOTEMatch your room size and your room's condition to the chart.
  1. Match your room area to a size group: under 2,000 square feet, or 2,000 square feet and over.
    <1m
  2. Read the recommended pint-per-day range for your size group and the condition you judged before.
    • Slightly to moderately damp, under 2,000 square feet: 20 to 30 pints per day.
    • Slightly to moderately damp, 2,000 square feet and over: 30 pints per day or more.
    • Very damp, under 2,000 square feet: 25 to 40 pints per day.
    • Very damp, 2,000 square feet and over: 40 pints per day or more.
    • Wet, under 2,000 square feet: 30 to 50 pints per day.
    • Wet, 2,000 square feet and over: 50 pints per day or more.
    1m
  3. Choose a dehumidifier with a pint rating at or above the top of your range.
    • A higher rating takes out moisture faster.
    • ENERGY STAR states that an oversized dehumidifier costs less than an undersized dehumidifier.
    <1m

Choose a portable or a whole-home dehumidifier

Estimated 2 min

NOTEA whole-home dehumidifier uses your duct system. A portable dehumidifier serves one room.
Minimum recommended operating air temperature, compressor dehumidifier
Manufacturer or standard verified
65 F

Source: Dehumidifiers · tier 1 · accessed 2026-08-04

Whole-home ducted dehumidifier sizing calculation
Unverified — do not rely on this value
CONSULT A HEATING AND COOLING CONTRACTOR FOR A DUCT-SYSTEM SIZING CALCULATION

No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.

  1. Choose a portable dehumidifier for one room with a door that closes.
    <1m
  2. Consider a whole-home dehumidifier for a humid house with central air conditioning.
    • ENERGY STAR describes this case as a house with central air conditioning.
    • The relative humidity in the house is above 55 percent throughout.
    <1m
NOTICE

DO NOT SIZE OR INSTALL A WHOLE-HOME DEHUMIDIFIER YOURSELF.
A professional sizes and fits a whole-home dehumidifier to your duct system. A wrong fit can let moisture reach the building frame.

  1. Hire a professional to fit a whole-home dehumidifier to your ducts.
    <1m
  2. Find the dehumidifier's minimum rated temperature before you buy it for a cold space.
    • A standard compressor dehumidifier can form frost when the air is below 65 degrees F.
    • This operating limit is not the test temperature named earlier in this page.
    • The two facts use the same number for different reasons.
    • Choose a dehumidifier rated for lower temperatures for a cold garage or an unheated space.
    <1m
  3. Find the water removal method before you buy: a bucket you empty, or a hose to a drain.
    • You must empty a bucket by hand.
    • A full bucket stops the dehumidifier automatically.
    • A hose sends water to a floor drain or a sump pump.
    • You do not need to empty a hose.
    <1m

Terminology

This page uses one term for each item and holds it throughout, as ASD-STE100 requires. Equipment sellers and other guides use the names below for the same parts.

dehumidifier capacity
Also called: pint rating, dehumidifier size, how many pints do I need, 50 pint vs 30 pint dehumidifier, dehumidifier pints per day
relative humidity
Also called: room humidity, how damp is my room, RH percentage, humidity level
whole-home dehumidifier
Also called: ducted dehumidifier, central dehumidifier, whole house dehumidifier, HVAC dehumidifier
portable dehumidifier
Also called: room dehumidifier, standalone dehumidifier, bucket dehumidifier
room floor area
Also called: room size, square footage, square feet, floor space

When to use a professional

Call a heating and cooling contractor to size and install a whole-home dehumidifier. Call the manufacturer for a room with an open floor plan, an unusual shape, or a connection to another room. Call the manufacturer if your room's condition is worse than the wet row in the chart.

Common questions

What size dehumidifier do I need?

It depends on your room's floor area and how damp the room is without a dehumidifier running. ENERGY STAR publishes a chart with two room-size groups (under 2,000 square feet and 2,000 square feet and over) crossed with three dampness levels, each with a recommended pint-per-day range. Measure your room, judge its condition, and read the range from the chart. Choose a unit at or above the top of the range, because ENERGY STAR says it is better to oversize than to undersize.

Why did the pint rating on dehumidifiers get smaller a few years ago?

The U.S. Department of Energy changed the official test in 2019. The old test rated a dehumidifier's moisture removal in 80-degree air; the new test uses 65-degree air, which is closer to a real basement. Cooler air holds less water, so the same physical machine reports a lower pint number under the new test. A lower number does not mean a smaller or weaker dehumidifier — it means a different, more realistic test.

Is a 50-pint dehumidifier from 2015 the same as a 50-pint dehumidifier today?

No. The 2015 unit was rated under the old, warmer test. ENERGY STAR's own correlation table puts a pre-2020 50-pint rating at about 30 pints under the current test. If you are comparing an old unit to a new one, use that table, or judge the old unit by how much water you actually empty from it each day rather than by the number printed on it.

My basement smells musty and has laundry drying in it. What size do I need?

Laundry drying indoors is one of the conditions ENERGY STAR lists under its wettest category, alongside walls or floors that sweat or visible seepage. For that condition, the chart recommends 30 to 50 pints per day in a room under 2,000 square feet, and 50 pints per day or more in a larger space. A musty smell alone, with no standing moisture, is the lighter "slightly to moderately damp" category instead.

Should I buy a portable dehumidifier or a whole-home system?

A portable dehumidifier is the usual choice for a single room or a basement with a door that closes. A whole-home, duct-connected dehumidifier is worth considering if your house has central air conditioning and stays above about 55 percent relative humidity throughout, but ENERGY STAR is clear that it needs a professional to size and install it correctly. This page does not size a duct system.

Can I use a regular dehumidifier in an unheated garage?

Check its rated minimum operating temperature first. ENERGY STAR warns that frost can form on a standard compressor dehumidifier's coils once the air drops below 65 degrees F, which stops it removing moisture properly. That is a separate fact from the 65-degree test temperature discussed elsewhere on this page — one is about where the machine is used, the other is about how its box number was measured. For a cold space, look for a unit rated for lower temperatures.

What does "pints per day" actually measure?

It is the amount of water the dehumidifier removes from the air over 24 hours under the government's test conditions, not a tank size or a bucket size. ENERGY STAR describes it as the dehumidifier's "size" for shopping purposes. Two dehumidifiers with the same pint rating, tested under the same current procedure, remove moisture at roughly the same rate.

Sources

Every specification on this page is traced to one of these sources. Tier 1 is a manufacturer document, a published standard, or a government safety authority. See Standards for the full tiering rule.

  1. Tier 1DehumidifiersENERGY STAR (U.S. Environmental Protection Agency, with the U.S. Department of Energy) · accessed 2026-08-04 · re-verification due 2027-01-31
  2. Tier 1Dehumidifier Testing and CapacityENERGY STAR (U.S. Environmental Protection Agency, with the U.S. Department of Energy) · accessed 2026-08-04 · re-verification due 2027-01-31

Revision history

Current version 1 · updated 2026-08-04 · next review due 2027-08-04

  1. v1 · 2026-08-04First draft. Sizing chart and the 2019 test-procedure change both sourced to ENERGY STAR (energystar.gov), read directly on 2026-08-04. The old-to-new capacity correlation table is quoted from ENERGY STAR's own published table. Whole-home duct sizing publishes as consult-a-contractor rather than a number; the operating-temperature spec is the only verified numeric specification and is kept explicitly distinct from the unrelated 65-degree test-condition fact.

Corrections to this page are listed in the public corrections log. Reports that are credible and not yet verified are listed in the public errata register, and an open one renders above the step it concerns.

Comments and corrections

Found an error? A correction with a manufacturer source is applied and logged publicly. You can also write to corrections@fixchecklist.com.

Every step above carries its own report control, which tags the report with that step so a correction reaches the right place. For anything about the procedure as a whole — the order of the sections, a step that is missing, something that did not match your equipment — use this: report something about this whole procedure.

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