How dehumidifier capacity is rated
Dehumidifiers are sized by how many pints of water they can remove in 24 hours. In 2019 the US Department of Energy changed the test: units are now measured at 65 °F and 60 % relative humidity – conditions typical of a basement – instead of 80 °F. Because cooler air holds less water, the same machine now gets a lower number. A model once sold as "70 pints" is labeled about "50 pints" today. DampCheck shows both, so you can compare older reviews and charts with current products.
Sizing chart (old 80 °F rating)
| Area | Moderately damp | Very damp | Wet | Extremely wet |
|---|
| 500 sq ft | 10 | 12 | 14 | 16 |
| 1,000 sq ft | 14 | 17 | 20 | 23 |
| 1,500 sq ft | 18 | 22 | 26 | 30 |
| 2,000 sq ft | 22 | 27 | 32 | 37 |
| 2,500 sq ft | 26 | 32 | 38 | 44 |
Add about 5 pints if a washer and dryer are in the space, and another 5 if more than two people regularly use it. Multiply by roughly 0.7 to convert to the current DOE rating.
Where dehumidifiers help most
- Basements: cool walls and ground contact keep humidity high – the most common use.
- Crawl spaces: encapsulated crawl spaces need a dedicated, ducted dehumidifier with a drain.
- Humid climates: in the Southeast, a whole-house unit connected to the HVAC system controls humidity year-round.
- Laundry rooms and bathrooms without good ventilation.
Features to look for
- ENERGY STAR certification – about 15 % more efficient than standard models.
- Continuous drain or built-in pump so you never empty a bucket.
- Low-temperature operation with auto-defrost for basements below 65 °F.
- Accurate humidistat and auto-restart after power cuts.
- Washable filter and caster wheels.
Target humidity
Keep indoor relative humidity between about 30 % and 50 %. Above 60 % for long periods, mold, mildew and dust mites thrive and wood can warp. Below 30 % air feels dry and static builds up. A cheap hygrometer helps you check the dehumidifier's built-in reading.
Frequently asked questions
What size dehumidifier for a 1,000 sq ft basement?
A very damp 1,000 sq ft basement needs about 17 pints on the old rating – about 12 pints on today's DOE rating, so the smallest current models (20 – 22 pints) are enough. Choose 30 – 35 pints for larger or wetter basements.
Why are new dehumidifiers rated lower?
Since 2019 they are tested at 65 °F instead of 80 °F. A new 50-pint unit removes about as much as an old 70-pint unit.
What humidity should a basement be?
Aim for 30 – 50 % relative humidity, and keep it below 60 % to prevent mold.
How much does it cost to run a dehumidifier?
Typically $10 – $40 per month depending on size, efficiency, hours and electricity price.
Is a bigger dehumidifier better?
A slightly larger unit dries faster and cycles less, but very oversized units cost more. Choose the size for your conditions.
About DampCheck
DampCheck is an independent, free sizing calculator for home dehumidifiers based on AHAM sizing guidance and the 2019 US Department of Energy test procedure. We are not affiliated with any appliance brand.
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