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Cool basement? Compressor vs desiccant
Updated
For a basement that stays around 60°F or warmer, a compressor dehumidifier with auto defrost is still the right tool. Buy one size up. For a small space that drops near freezing, such as a camper in storage or an unheated bathroom, a desiccant unit works where a compressor unit cannot.
Why cool air is hard on compressor units
A compressor dehumidifier works like a refrigerator. Damp air passes over cold coils, water condenses on them and drips into the bucket. Two things go wrong as the room gets cooler.
- Less water comes out. Cool air holds less moisture, so there is less to catch. This is the whole reason the 2019 test change, from 80°F to 65°F, turned 70-pint units into 50-pint units.
- The coils frost over. In a cool room the coils drop below freezing and ice builds up. Auto defrost stops the compressor and runs the fan until the ice melts. The AlorAir HD55 listing describes exactly that. While it defrosts, the unit is not drying anything.
The home units on my list, the hOmeLabs 50 Pint, the Midea Cube and the Waykar, all name auto defrost on their listings. None of those listings gave me a minimum working temperature, so check the manual for your model. Many compressor units are not meant for rooms much below the low 40s.
What a desiccant unit does differently
A desiccant dehumidifier has no cold coils. A slowly turning wheel soaks up moisture from the air, and a heater dries the wheel back out. Nothing can frost. The Ivation 13-Pint Desiccant lists a working range of 33°F to 104°F.
The catch is power. It takes heat to dry the wheel.
| Model | Type | Listed pints per day | Listed watts | Rough pints per kWh |
|---|---|---|---|---|
| hOmeLabs 50 Pint | Compressor | 50 | 322 | 6.5 |
| Midea Cube 20 Pint | Compressor | 20 | 214 | 3.9 |
| Ivation Desiccant | Desiccant | 13 | 470 | 1.2 |
| Pro Breeze Mini | Mini, no compressor | About 0.56 | 23 | 1.0 |
These are rough. I divided each listing's pints per day by the power it would use running around the clock, and the listings measure pints at different temperatures. The pattern still holds. In a mild room, a compressor unit removes several times more water per kWh. A desiccant unit earns its place only where a compressor unit would sit frozen. It also blows warm air, which owners notice. That is welcome in a cold camper and a nuisance in July.
What about the little mini units?
At 23 watts and 2.4 pounds, the Pro Breeze Mini is not a compressor machine, and it is not a cold-room answer either. Its listing says it works best from 59°F to 86°F and will not work below 41°F.
Which to buy
| Your space | What I'd pick |
|---|---|
| Basement, 60°F and up most of the year | Compressor unit sized by the calculator |
| Basement in the 50s for months | Compressor unit with auto defrost, one size up. Expect slower drying in winter, when the air is also drier |
| Crawl space | A unit built for it, like the AlorAir HD55. Its listing names low-temperature operation and auto defrost |
| Small space near freezing | Ivation Desiccant, within its 270 sq ft rating |
Tick the "below 65°F" box in the size calculator and it moves you up a class for this reason. One more thing: if pipes in the space could freeze, that is a heating and insulation problem. A dehumidifier will not solve it.