What Size Dehumidifier Do I Need?
Pick the capacity from how damp the space is and how big it is, using ENERGY STAR's chart below, and read any pint rating with the 2019 test change in mind. Both matter, because a listing's number can be off by a lot depending on which test produced it.
In 2019, the U.S. Department of Energy's revised test procedure for dehumidifiers took effect. The specific change: the test temperature dropped from 80°F to 65°F, to better represent a basement environment. Cooler test air holds less moisture, so the same physical unit measures a lower pint-per-day rating under the new test than it would have under the old one. The unit didn't get weaker, the test got colder.
That means a dehumidifier rated 30 pints today is not necessarily weaker than an older unit rated 40 pints: the numbers were produced under different test conditions and aren't directly comparable without knowing which standard applies. ENERGY STAR's own published correlation gives a sense of scale: a unit that would have rated around 60 pints under the old test rates around 35 pints under the new one, roughly the same physical machine, a different number.
Source: ENERGY STAR, Dehumidifier Testing and Capacity.
Find the rating year, not just the number
Check the product's spec sheet or ENERGY STAR listing for the test standard or certification date. A listing that has been live, unchanged, since before 2019 may still be citing the old test's number. Treat that figure as not directly comparable to a newer listing's rating until you confirm which standard was used.
ENERGY STAR's dehumidifier size chart
ENERGY STAR sizes by two things: the condition of the space without a dehumidifier, and whether the area is under or over 2,000 square feet. Its own descriptions of each condition:
| Condition without a dehumidifier | Under 2,000 sq ft | Over 2,000 sq ft |
|---|---|---|
| Slightly to moderately damp: feels damp, musty odor that may come and go, 50 to 75% RH | 20 to 30 pints/day | 30+ pints/day |
| Very damp: consistently feels and smells damp, damp spots on walls and floors, 75 to 90% RH | 25 to 40 pints/day | 40+ pints/day |
| Wet: walls or floor sweat or seepage is present, or high loads such as drying laundry, 90 to 100% RH | 30 to 50 pints/day | 50+ pints/day |
ENERGY STAR's advice when you're between sizes: it's better to oversize than undersize. The RH ranges are what a hygrometer reading tells you, so measure for a few days before choosing a row. Seepage and standing water belong to the last row, but they also mean the source needs fixing; see crawlspace moisture and preventing basement mold.
The chart doesn't say which test year its pint figures assume. Use it to pick a range, then compare listings that were rated under the same procedure, as explained above.
Placement and cold rooms
- Keep the unit away from walls and furniture so air can circulate around it, and keep the doors and windows of the space closed while it runs. Both are ENERGY STAR's own placement advice.
- Cold rooms cut performance: ENERGY STAR notes that frost can form on the coils when the air drops below 65°F, and some units have an anti-frost sensor for that reason. In a cold basement or garage, check that the model handles low temperatures before relying on its rating.
Source: ENERGY STAR, Dehumidifiers (sizing chart, placement and frost advice), read October 5, 2026.