Finding the right size dehumidifier is critical for maintaining a healthy home environment. If the unit is too small, it will run constantly without ever reaching your target humidity. If it is too large, it may cycle on and off too frequently, leading to premature wear and inefficient energy use.
*Based on DOE 2020 testing standards (65°F and 60% RH).
How Dehumidifier Sizing Works
Dehumidifiers are rated by the number of "pints of water" they can remove from the air in a 24-hour period. However, it is important to note that the Department of Energy (DOE) updated its testing standards in 2020. Modern units are tested at lower temperatures, meaning a new "50-pint" unit is roughly equivalent to an old "70-pint" unit.
Understanding Dampness Levels
To use the calculator effectively, you need to accurately assess the moisture level of your space:
- Moderately Damp: The space feels humid and has a musty odor only during particularly damp or rainy weather.
- Very Damp: The space always smells musty and feels damp. You might notice slight damp spots on the floor or walls.
- Wet: You can see moisture on the walls or floor. There is visible seepage, and the air feels very heavy.
- Extremely Wet: This is for basements or rooms with standing water, extreme mold growth, or laundry being dried in an unventilated space.
Factors That Increase Capacity Needs
While square footage is the primary driver, several other factors may require you to "size up" your dehumidifier:
- High Ceilings: Most calculations assume an 8-foot ceiling. If your ceilings are 10-12 feet, add 10-20% to the recommended capacity.
- Climate: If you live in a region with consistently high outdoor humidity, a larger unit will handle the load more effectively.
- Multiple People: Every person living in the space adds moisture to the air through breathing and perspiration.
- Open Floor Plans: If the room is open to other areas of the house, the dehumidifier will end up trying to dry the air in those rooms as well.
Why You Shouldn't Buy the Smallest Unit
It is often tempting to buy the smallest (and cheapest) unit that fits your square footage. However, a larger unit will reach the target humidity faster and then shut off. This "cycle" is often more energy-efficient than a small unit running 24/7. Additionally, larger units often have larger water buckets, meaning you have to empty them less frequently if you aren't using a continuous drain hose.