How Long Should You Keep A Dehumidifier On?

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If you keep noticing condensation on your windows, it's a sign that you might need a dehumidifier. Even worse, if you're smelling musty odors and starting to notice mold growth, peeling paint, or warped wood, those are surefire signs you should run a dehumidifier in your house. But how do they work exactly, and how long do they need to run in order to be effective?

As the name implies, a dehumidifier is an appliance that removes moisture from the air. It draws in humid air and converts its moisture to condensation, then puts out drier air to bring humidity levels lower. The Environmental Protection Agency recommends keeping indoor relative humidity levels between 30% and 50%. Below this range, you may run into nasal congestion or worsened eczema. Above this range, you're likely to see the previously mentioned problems like mold and paint peeling. To prevent these issues, it's best to start running your dehumidifier when humidity levels surpass 50%. How many hours it needs to run to bring those levels back down depends on a few things, but you can generally expect to run the machine for around 8 to 12 hours per day to keep humidity within the ideal range.

There are a few factors affecting how long a dehumidifier will need to run. Some dehumidifiers are more efficient, in which case moisture levels should come under control more quickly. Check your dehumidifier's capacity, which refers to how many pints of water it can remove from the air over 24 hours. Another thing to consider is choosing the right size dehumidifier for your space; the bigger the room, the more air it will need to process. The temperature of the room also matters since relative humidity measures how moisture-saturated the air is at a given temperature. Cooler air can hold less water, leading to higher relative humidity, even if the amount of water in the air remains unchanged — because of this, cooler rooms can take longer to dehumidify.

While the general recommendation may be to run your dehumidifier for 8 to 12 hours per day,
the real answer is to keep it running until your home's humidity is consistently within the 30% to 50% window. Some dehumidifiers feature a small screen displaying the current humidity levels and can run on a timer. If yours doesn't have this, a hygrometer like this SMARTRO SC42 Professional Digital Hygrometer can help you check the humidity levels in your home. You can even get a humidistat, which works with your HVAC system and acts as a thermostat for indoor humidity levels. Whatever dehumidifier you're using, you'll get a sense of how long to run it after a few test runs at home. And remember, not everyone is the same. The ideal range is wide enough for you to find the exact humidity level that's most comfortable for you.