What size dehumidifier do you need?
Pick the room and how damp it is, get the pints per day ENERGY STAR recommends.
Slightly to moderately damp: feels damp, musty odor that comes and goes. Very damp: consistently damp and musty, damp spots on walls and floors. Wet: sweating walls or floor, seepage, or heavy loads such as drying laundry.
ENERGY STAR lists portable units from 30 to 90 pints and whole-home units from 80 to 200 pints; other values show the two rows around them.
Measure with the old unit running as usual. If its bucket fills and it shuts off, the real need is higher.
What size dehumidifier do I need?
ENERGY STAR sizes a portable dehumidifier by how damp the space is and by whether the room is under or over 2,000 square feet. For a room under 2,000 ft², it recommends 20 to 30 pints a day if the space is slightly to moderately damp (it feels damp and has a musty odor that comes and goes, 50–75% relative humidity), 25 to 40 if it is very damp (it consistently feels and smells damp and has damp spots on walls and floors, 75–90%), and 30 to 50 if it is wet (walls or floor sweat, seepage, or heavy loads such as drying laundry, 90–100%). For rooms over 2,000 ft² the figures are 30+, 40+ and 50+. A musty 800 ft² basement that is damp most of the time lands at 25 to 40 pints. ENERGY STAR adds that it is better to oversize than undersize. Its table splits only at 2,000 ft², so there is no pints-per-square-foot rule to scale.
Why do new dehumidifiers have lower pint ratings than old ones?
The U.S. Department of Energy changed the test. Since the June 2019 standards, portable dehumidifiers are rated at 65 °F and 60% relative humidity instead of 80 °F, and whole-home units at 73 °F. Cooler air holds less water, so the same machine gets a smaller number. ENERGY STAR gives a rough match for portable units: 30 pints before 2019 is about 20 now, 40 is 25, 50 is 30, 55 is 30–35, 60 is 35, 70 is 40–45 and 90 is 55. For whole-home units: 80 is 70, 100 is 85, 120 is 100, 140 is 115, 160 is 135 and 200 is 170. ENERGY STAR calls the table rough and says the change for a particular model varies, so ask the maker if the choice is close.
Which rating does the ENERGY STAR sizing table use?
ENERGY STAR does not say. The table sits in its current buying guide, right after a note that the capacity options have changed. Archived copies of the page from 2016 to 2019 do not have the table, and a copy from May 2020 does, so it dates from about the time the new ratings reached the stores. That suggests the ranges fit the pints-per-day numbers printed on current boxes, but ENERGY STAR does not state it. For a unit rated before 2019, convert its rating first, and when a room sits on the line between two ranges, take the larger one, as ENERGY STAR advises.
How do I pick a replacement from what my old dehumidifier collects?
ENERGY STAR's advice for replacing a unit is to judge by how much water you empty each day. Add up what you empty and divide by the days: 36 pints emptied over 2 days is 18 pints a day, or 8.5 liters (a U.S. pint is 0.4732 liter). If the bucket fills and the machine shuts itself off, what you emptied understates what the room needs, so size up. Use the “Water I empty” tab, then compare with the ENERGY STAR ranges.
Does the room temperature matter?
Yes. ENERGY STAR notes that frost can form on the coils when the air stays below 65 °F, which can make the compressor cycle without removing moisture, and suggests a model specified for lower temperatures in a cool basement. DOE chose the 65 °F test condition to reflect a basement (it expects the average ground temperature in the dehumidifying season to be close to 65 °F), so a rated capacity describes a cool basement, not a warm summer room.
Sources: ENERGY STAR, “Dehumidifiers” (Buying Guidance, Capacity) and “Dehumidifier Testing and Capacity”, energystar.gov, read October 7, 2026, with archived copies of the first page from May 2019 and May 2020; U.S. Department of Energy, Federal Register Vol. 80, No. 147 (July 31, 2015), “Energy Conservation Program: Test Procedures for Dehumidifiers”. A U.S. liquid pint is 0.473176473 liter (NIST Handbook 44). Moving air: CFM calculator; whole-house ventilation: ventilation rate calculator; cleaning the air: air purifier size calculator; humid attics: attic ventilation calculator. How we check our calculators.