When Should You Use a Dehumidifier: 6 Reasons You Need One

Recommended Dehumidifiers for Each Room


Dehumidifiers aren’t exactly the cheapest device to run in your home, especially if you’re trying to cover a large, damp, and cold space. At the same time, dehumidifiers can save your health and prevent you from having to spend thousands of dollars in the future to remediate mold. The decision to either use a dehumidifier or not can be quite consequential.

So, when should you use a dehumidifier? You’ll mostly use a dehumidifier in the late spring, summer, and early fall. Some climates and homes tend to have higher levels of humidity, so you’d need a dehumidifier in those instances. Dehumidifiers can help eliminate existing mold issues but should be seen as a way to prevent mold in the future in your home as well.

There are many situations and specific times during which you’d need a dehumidifier. Let’s take a look when it makes sense to run a dehumidifier.


When to Use a Dehumidifier

Not everyone needs a dehumidifier, but here are some of the main reasons when you’ll definitely need to use one.

  • Your home has high humidity levels.
  • You can afford it.
  • You have a basement.
  • It’s late spring to early fall.
  • You live in an area with high humidity.
  • You have mold issues or want to prevent them in the future.

Your home has high humidity levels.

It seems obvious to use a dehumidifier when your room is damp, but there’s more to it.

Humidity is measured in terms of relative humidity (RH), which is simply a function of how much moisture is in the air at any given temperature compared to the overall environment. It’s the same measurement that meteorologists use to tell us the chance of rain on any given day.

The RH inside a home needs to stay between 30% and 60%.

30% is the minimum needed to stay hydrated enough to live inside a home, but this side of the RH spectrum is rarely an issue in most American homes. You’ll notice this if you have a dry throat and dry eyes. If this is the case, you’ll need a humidifier, not a dehumidifier!

Once your RH level gets above 50% to 60%, however, enough moisture exists for mold to form and thrive. This is what most people are concerned with. It’s just a matter of time when mold will form if the RH levels are 70% or above.

To take those measurements, you’ll need a hygrometer.

But of course, not everyone has a hygrometer to measure the exact levels of RH. Oftentimes these levels will fluctuate depending on how moist the air outside is, too. But you can get a general sense of whether your home’s interior is humid or not even without the use of a hygrometer. Here are a few ways to tell if there’s excess moisture in your home:

  • If the room has a musty smell, that’s the first sign you need a dehumidifier, immediately. A musty smell is also a sign of the presence of mold, so you’ll need to take additional steps to rid the room of mold besides just buying a dehumidifier.
  • Laminate flooring that all of a sudden is starting to make a squeaky sounds and has warped edges is a sign that the moisture in the air is destroying your home slowly.
  • Look at the corners of your walls and ceilings to see if you can spot patches of mold or moisture.
  • Moisture tends to seep underneath wallpaper and latex paint on the walls. Is your wallpaper peeling off and are bubbles forming under the latex paint?
  • If you have wood surfaces or wood crown molding, look for signs of it rotting.
  • Condensation is one of the major signs of moisture. Are your window panes full of moisture or can you see through the window clearly? Place a clear glass in your living room or bedroom and fill it with a few ice cubes. Does the melted water condense on the outside of the glass to the point that droplets are running down the side of the glass, or can you see through the glass like you normally would? If it’s the former, you have a moisture issue.
  • You might have a dripping pipe somewhere or If the pipes are starting to rust, that’s even more proof of excess moisture.


You can afford it.

Dehumidifiers can add on to your monthly electricity bill, so you’ll first have to decide if a dehumidifier is in your budget. If your home has high levels of humidity, your dehumidifier will need to run at least 12 hours every day, so you shouldn’t expect it to be the kind of appliance that only runs occasionally.

Not only do you need to understand the cost to run a dehumidifier, but you also need to know just how large and how powerful the dehumidifier needs to be.

Dehumidifier capacities are rated based on how many pints of water the dehumidifier can remove in any given 24-hour period. Unfortunately, manufacturers are notorious for misrepresenting the capacity of their dehumidifiers by using testing standards that are most convenient for them and not necessarily representative of an average home environment.

This leads most homeowners to choose a dehumidifier that isn’t powerful enough for their home. Once you do the research, you’ll quickly realize that that dehumidifier that was advertised to be able to remove 15 pints of water per day actually can only do a fraction of that once it’s in your home. You’ll also quickly realize that the dehumidifier you really need is more expensive, too.


You have a basement.

Basements are commonly more humid thanks to their contact with the damp soil. Quite frankly, there are very few basements that don’t need a dehumidifier. Basements can run the gamut when it comes to humidity levels, with some having a relative humidity (RH) as high as 95%!

Save yourself the hassle of having to pay thousands of dollars in the future to remediate mold and get a dehumidifier to keep mold at bay.

Just make sure that the dehumidifier is powerful enough and is rated to remove an amount of water that’s well above the square footage that the manufacturer recommends for it. If you don’t do this, the coils inside the dehumidifier will constantly be frozen and make the dehumidifier useless for you.

It’s late spring to early fall.

Since most winters have drier air, a dehumidifier will mostly be dormant during that time. However, once the spring arrives, you can expect your dehumidifier to kick into high gear and to virtually be on the entire summer.

The table below represents how often and when a dehumidifier will run in the Northern Hemisphere, as suggested by the US Department of Energy (DOE). The information is presented as operating hours, meaning the total time when both the fan and coils are running in the dehumidifier.

MonthOperating Hours



This should be taken with a grain of salt because it assumes a home environment of 80 ºF and 60% RH. Most homes will require their dehumidifier to operate more often than what’s suggested here, but the idea is still the same.

One word of advice you may wish to heed after the “dehumidifier season” is over in the fall –

Dehumidifiers have coils inside that can freeze over in cold temperatures. If you aren’t going to run the dehumidifier during the winter, take great care to properly clean and maintain it. You may also wish to stash it away on an upper level in your home where it’s warmer during the winter.


You live in an area with high humidity.

The outside air will play a major role in when your dehumidifier runs and if you even need to get one in the first place. If the RH in your climate tends to persist at 60% and above, remember that your home will be ideal for mold growth.

If you live in the United States, you might be surprised to find out that much of the country’s climate sits at a 50% RH level or higher, even during the winter months.

If you set the dehumidifier on its auto setting and your area is prone to constant rain, you’ll realize quickly that the dehumidifier virtually never shuts itself off. It may not be apparent at first as the dehumidifier will spend more time running during the night and early morning before you awaken than during the day. Just be mindful that it can take a toll on your electricity bill during those times of the season.


You have mold issues or want to prevent them in the future.

If you’re already experiencing mold in your home, you need a dehumidifier immediately. Hopefully, the mold hasn’t gotten out of control yet and you can still eliminate it on your own. If the mold is in the basement, there are several methods to get rid of the mold besides just the dehumidifier. Use this article as a guide to help you purify the air in your basement and get rid of the mold.

If you don’t have a mold issue yet, I definitely recommend a dehumidifier to prevent the mold. Also, organic surfaces like the adhesive behind wallpaper, wooden furniture and insulation are notorious for attracting mold. Try to eliminate or clean what you don’t need in the space to make the environment less friendly to mold.



I hope I have helped you decide whether you need a dehumidifier or not, and when you should run it.

If your home is ready for it, here are my recommendations to help you find the dehumidifier that’s right for you.