All about dehumidifiers (FAQ)

This article answers all of the most common questions about dehumidifiers.

The following questions are being discussed, you can use the links to jump to the questions.

Are you considering purchasing a dehumidifier? I recommend reading my article on the pros and cons of dehumidifiers.



How do I know if I need a dehumidifier?

To find out if you need a dehumidifier, check for the following conditions and symptoms in your house:

  • the air feels damp and clammy
  • the air smells musty
  • you have condensation on walls and windows
  • you find tiny, dark mold and mildew spots
  • dust mites are prevalent
  • your allergies are triggered often
  • your laundry dries very slowly when hung inside
  • papers, books, and paintings start to crook
  • a hygrometer regularly reads a relative humidity above 60%
  • wood starts rotting
  • iron starts rusting

High humidity can cause all of the abovementioned symptoms and a dehumidifier will help solve these issues. The most comfortable humidity levels are between 40 and 50% relative humidity. This can be measured by a hygrometer which is often included in a simple thermometer. Some dehumidifiers will also show the percentage of humidity in your air and can be set to lower the humidity to the desired level. You can find good dehumidifiers on amazon.com.


Does a dehumidifier clean the air?

A dehumidifier helps make the air cleaner without actively removing harmful substances from the air. Humid air is more stagnant, trapping harmful and odor-causing particles, therefore making the air less healthy to breathe. By using a dehumidifier, the air becomes less humid and stagnant, allowing for better ventilation. Therefore, a dehumidifier can improve airflow and help provide fresh clean air.

So, a dehumidifier does not remove harmful particles from the air. For this, you need an air purifier. A dehumidifier does, however, remove moisture from the air, making the air less humid. Since humid air is more stagnant, high humidity results in less healthy air since harmful particles are not as easily ventilated out.

According to the United States Environmental Protection Agency (US EPA), indoor air is often 2 to 5 times more polluted than outdoor air. Ventilation is key to maintaining healthy indoor air. However, if your indoor air has a humidity above the optimal 40-50%, your air is more stagnant and will not as easily be ventilated. Therefore, although not actively removing harmful particles from the air, a dehumidifier helps improve indoor air quality. It makes the air less humid, and less stagnant, therefore allowing for better ventilation.


Can a dehumidifier kill mold?

A dehumidifier does not remove mold that is already present, nor does it filter mold spores from the air. However, a dehumidifier prevents mold from establishing and halts already growing mold from expanding. This is done by lowering the humidity and preventing condensation. A dehumidifier makes sure humidity levels do not reach levels above 60%, the ideal condition for mold growth.

To remove mold, the mold spots need to be removed and the surface cleaned. A dehumidifier then prevents molds from establishing by not allowing the air to reach a relative humidity above 60% and by preventing condensation.


Do I need a dehumidifier if I have an air purifier?

An air purifier removes harmful substances like fine dust and VOCs from the air while a dehumidifier reduces its moisture content. An air purifier is not able to reduce the humidity of the air. Therefore, if you have humid air, above 50% relative humidity, you will need a dehumidifier to create the most healthy and comfortable air in your home.

To create the most healthy air indoors while you have issues with high humidity, you will benefit from having both a dehumidifier and an air purifier. Symptoms related to high humidity include the presence of molds and mildew, condensation on walls and windows, and the air feeling damp and clammy.


Will a dehumidifier cool down a room?

A dehumidifier does not cool down the room since it does not lower the temperature of the air. However, a dehumidifier lowers the humidity of the room. Because of this, cold rooms feel warmer and warm rooms feel cooler.

A dehumidifier lowers the relative humidity of the air by removing water vapor. Because of this, your body is better able to sweat in order to lose heat, making a warm room feel cooler. Also, in cold rooms, lowering the moisture content of the air with a dehumidifier makes you feel warmer. This happens because your skin is less exposed to ‘wet’ air, which feels cold. In this way, a dehumidifier improves thermal comfort.


How much electricity do dehumidifiers use?

A standard 1000 to 2000 sq. ft. dehumidifier uses, on average, 125 watts. The smallest dehumidifier uses at least 48 watts and a large dehumidifier can use up to 425 watts. Running a 125 W dehumidifier for an hour will consume 0.125 kiloWatt-hour (kWh) of energy. Using different settings on the device determines the exact number of watts that are being used. Since dehumidifiers should be run constantly, they will consume, on average, 3 kWh per day, or 90 kWh per month.

Dehumidifiers, like all appliances, have a label that shows their wattage. The number of watts that an appliance uses is the amount of energy it uses when running for one hour. So for example, my 200 watts dehumidifier uses 200 Watts, 0.2 kW, when running for one hour. The amount of energy used is then 0.2 kWh (kiloWatt-hour).

This is, however, not the exact amount of electricity that they use all the time, but the maximum amount they can use, according to energy.gov.

For example, my 200 Watts dehumidifier, even when running at maximum speed, uses about 163 Watts. The picture below is a screenshot of its energy use as I’m writing.

Dehumidifier energy use, app screenshot

I got this energy use information from an app that is connected to a smart socket. This socket can show details like energy use but is also able to set a timer to turn the socket, and therefore the attached device, on or off. I really like these smart sockets since I am able to turn my devices on and off with my smartphone or set a timer. You can find these kinds of smart sockets on amazon.com.

The following table shows the energy use of a variety of dehumidifiers. For more details and prices of these dehumidifiers, use the links in the table.

DehumidifierArea coverageEnergy use (on average)
Levoair330 sq. ft.48 W
Letsport480 sq. ft. 48 W
Inofia1000 sq. ft.125 W (max 205 W)
Yaufey1500 sq. ft.120 W (max 200 W)
Waykar2000 sq. ft. 128W (max 230 W)
Yaufey4500 sq. ft.195 W (max 320 W)
Table 1: Dehumidifiers’ energy use

A standard American living room is on average 330 sq. ft. Therefore, based on the table above, a dehumidifier for the living room will use about 48 watts. A typical American basement can be as large as the rest of the house. Therefore, 1000, 1500, or 2000 sq. ft. dehumidifier is often required. A 1000-2000 sq. ft. dehumidifier uses about 125 W.


Can you leave a dehumidifier on all night?

A dehumidifier can be run 24/7 and can run throughout the night. Features such as a shutdown when the tank is full, or a hose for continuous drainage make sure the device will not spill over when left unattended. A feature that allows you to set the desired humidity makes sure the air does not get too dry when it runs continuously.

I run my dehumidifier almost constantly, especially during the night when the relative humidity tends to increase due to dropping temperatures. This makes sure I am comfortable in the morning. On top of that, running my dehumidifier during the night allows me to quickly dry my laundry.


Will a dehumidifier make the room smell better?

A dehumidifier helps reduce musty odor and make your room smell better. By removing excess air moisture, mold spores in the air will become less common and their smell will be reduced. Additionally, lowering the room’s humidity allows for more airflow and ventilation, which removes stale, polluted, and bed-smelling air.

So, by lowering the humidity of the air, not only will you be able to more easily ventilate and allow for fresh air, but you will also reduce or eliminate the causes of bad smells. Especially mold and mildew spores create a musty odor. Mold and mildew prefer humid air (60% relative humidity and higher) and spots with condensated water. Therefore by lowering the humidity, you will prevent mold and mildew from growing and producing spores that make the air smell bad.


Should I turn my dehumidifier off in the winter?

If you live in an area where the winters are humid, you should continue to run your dehumidifier to improve thermal comfort and reduce humidity. When your winters have dry air, turning off your dehumidifier will make sure you maintain the level of humidity you have, resulting in the most comfort. You should turn off your dehumidifier when you have a compressor-type dehumidifier since it will freeze in temperatures below 65°F (18°C).

Depending on where you live in the world, your winters can either be very humid or relatively dry. For example, I live in the Netherlands where outdoor humidity is constantly high at around 80%. Therefore, in winter, to feel less cold, I need to run my dehumidifier to lower the humidity.

However, other parts of the world can have dry air during winter. When this is the case for you, running a dehumidifier will only make things worse and you should turn it off. Actually, many dehumidifiers will not even work in low-humidity conditions since the internal mechanism needs a relatively high air humidity.

Another consideration for turning off your dehumidifier during winter is the following:

  • you have a compressor-type dehumidifier (instead of a desiccant dehumidifier), and
  • the temperature of the room you are using it in often drops below 65°F (18°C)

If you meet both of these conditions, you risk freezing your dehumidifier. This makes it not able to function and can damage it.


Where should you place a dehumidifier?

A dehumidifier is best placed in the middle of the room in which you need to lower the humidity. This allows for optimal airflow and optimal working conditions for the device. For a specific area within a room that requires moisture removal, position the dehumidifier close to this spot while maintaining at least 12 – 14 inches (30 – 35 cm) of space around it to allow for the best airflow through its filters.

Additionally, the following conditions are recommended:

  • Select a firm and flat location for the dehumidifier, flimsy, or slanted surfaces may result in abnormal noise and vibrations
  • Do not place the dehumidifier closer than 4 inches (10 cm) to other objects
  • Make sure none of the openings are blocked, so air can circulate freely in, out, and around the unit
  • Do not place anything into any opening of the device
  • Don’t sit or place heavy objects on it
  • Do not plug the product into an electrical outlet or power strip that is being used by several other appliances. Use an electrical outlet dedicated to the product


Can you dehumidify too much?

A dehumidifier can reduce the humidity of the air to about 30 to 40% when run constantly at temperatures of at least 70 °F (21°C) (source). This leads to air that is too dry to be comfortable and can lead to symptoms of thirstiness, dehydration, and respiratory problems. A humidity of 40 to 50% is most comfortable. Using the feature to set the desired humidity or turning off the device is recommended when humidity levels drop below 40%.