Enter the floor area of the space and how damp it is, and the calculator gives you the dehumidifier capacity ENERGY STAR recommends, in pints per day on today’s labels. It also warns you when the space is too big for a single portable unit or too cold for a standard one.
Recommended capacity
25–40 pints/day
For spaces over 2,000 sq ft (about 185 m²), ENERGY STAR only gives a minimum: consider a larger or whole-home unit.
Below about 65 °F (18 °C), frost can form on the coils of standard models: choose one rated for low temperatures.
Based on the ENERGY STAR sizing chart, using the capacity ratings of the current US DOE test (since 2019). Older models were rated higher for the same machine. Nothing you enter is stored.
How to judge how damp the space is
- Slightly to moderately damp: the space feels clammy or smells musty only in humid weather.
- Very damp: it always feels damp and smells musty, and you see damp spots on walls or floors.
- Wet: walls or floors sweat, or water seeps in. Fix the water problem first: a dehumidifier cannot keep up with a leak.
A hygrometer helps you decide between two categories. The EPA recommends keeping indoor humidity below 60%, ideally between 30% and 50%.
The ENERGY STAR sizing chart
| Condition | Up to 2,000 sq ft | Over 2,000 sq ft |
|---|---|---|
| Slightly to moderately damp | 20–30 pints/day | 30+ pints/day |
| Very damp | 25–40 pints/day | 40+ pints/day |
| Wet | 30–50 pints/day | 50+ pints/day |
Replacing an older dehumidifier? The ratings changed in 2019
Since June 2019, portable dehumidifiers are tested at 65 °F instead of 80 °F, which lowers the rated capacity of the same machine. ENERGY STAR publishes this conversion, so don’t buy a new unit by matching the number on your old one:
| Old rating | Equivalent today |
|---|---|
| 30 pints/day | 20 pints/day |
| 40 pints/day | 25 pints/day |
| 50 pints/day | 30 pints/day |
| 55 pints/day | 30–35 pints/day |
| 60 pints/day | 35 pints/day |
| 70 pints/day | 40–45 pints/day |
| 90 pints/day | 55 pints/day |
Cold basements and energy use
ENERGY STAR warns that below about 65 °F frost can form on the coils of standard dehumidifiers, making the compressor cycle without removing much moisture. For a cold basement or crawl space, choose a model specified for low temperatures. ENERGY STAR certified models remove the same moisture as conventional units of similar size while using about 20% less energy.
Frequently asked questions
Is a bigger dehumidifier always better?
Not always. A larger unit dries the space faster and runs less often, but costs more to buy. In a very damp space, an undersized unit can run all day without reaching your target humidity, so when in doubt between two sizes, the larger is usually the safer choice.
Should I use square feet of the whole house?
No. Use the area of the space the dehumidifier will serve, such as the basement or one floor. Portable units move air poorly through closed doors and between floors.
What humidity should I set it to?
A setting between 30% and 50% matches the EPA’s recommended range. Going much lower wastes energy without extra benefit.
Sources
- ENERGY STAR. Dehumidifiers (sizing chart, low temperatures, energy savings).
- ENERGY STAR. Dehumidifier testing and capacity (2019 test change and conversion table).
- US EPA. A brief guide to mold, moisture and your home.