How Long Does it Take for a Dehumidifier to Work

When you use a dehumidifier for the first time, it can feel like forever for it to start working properly.

After all, it needs to warm up and then work out how much humidity already exists in your home. But how long does it really need to get started and provide you with drier air?


The good news is that you probably won’t need more than 12 hours before you get to start enjoying the benefits of your new dehumidifier.

However, before you get it working there are a few things you should keep in mind first. This guide takes you through everything you need to know so that you can run your dehumidifier in the best and most efficient way possible.

Pro Breeze 12L/Day Dehumidifier

How Long Does it Take for a Dehumidifier to Work?

Dehumidifiers regulate the humidity in a room by removing any excess moisture from the air, thereby creating a living condition that is inhospitable to dust mites, mould and other allergenic organisms. Out of the box, a dehumidifier can take up to 12 hours to start working properly and to get to the ideal level of humidity that your home needs.

Certain models can start working properly almost instantly, but some may need time to adjust to the environment around it.

Deciding the right humidity level can be determined by using a hygrometer. A hygrometer is relatively inexpensive and can be found at any local hardware store. Ideally, the humidity level in the home should be between 30 to 60%.

In areas that attract higher amounts of humidity, such as basements and crawl spaces, the setting should be set at 60% or less in order to prevent mould growth.

Additionally, don’t worry too much about getting the humidity settings exactly right. That’s not critical for the dehumidifier to work effectively. As long as the dehumidifier is in the right approximate range, it will work to help remove moisture effectively.


Dehumidifier Capacity and Size of Tank

Dehumidifiers come in different capacities, which refers to the amount of water the tank can collect, not how big the unit is. The most commonly used capacities are 15L, 30L, and 45L. However, it is possible to find both larger and smaller tanks. The higher the capacity, the more water that the unit can extract in the same amount of time.

Below is a chart determining the average amount of time taken to dehumidify a 50 sq. foot room at 27°C for each capacity from (a) 90% to 40% relative humidity and (b) 80% to 50% relative humidity.




12L34 minutes15 minutes
20L17 minutes8 minutes
30L11 minutes6 minutes

Air dehumidifiers with larger capacities do not have to work at full power to cover the same surface area, leading to lower energy costs for running it.

Dampness Level

You can purchase a hygrometer to measure the moisture levels in your home, by doing this you can also determine if your dehumidifier has a large enough capacity to collect the moisture in the room. Below is a chart with the minimum required capacity depending on the level of dampness, which also correlates to the size of the room in question.

Dampness Level

Capacity (Litres per 24 hours)

Area (sq. ft)

Moderately Damp


Highly Damp




Extremely Wet


How Long Should a Dehumidifier Run Per Day?

Dehumidifiers should run for at least 12 hours a day, this is also highly dependent on the room dampness level, the unit’s capacity, and built-in features. If the room condition is extremely damp, you might need to leave the dehumidifier on for the entire day as well as overnight.

To ensure that your home is safe while the machine is running this long, make sure to have a dehumidifier with an automatic shut off feature that will work when the dehumidifier becomes too full.

A way to avoid having to dump the dehumidifier every time it becomes too full is to connect a drainage pipe to the back and place it through a window or to a floor drain. This is a fantastic way to run your dehumidifier in a manner that is both safe and highly effective.

dehumidifier time

Do Dehumidifiers Lose Effectiveness Over Time?

Like all appliances, dehumidifiers also have a lifespan and will usually last close to a decade. Running the dehumidifier 24 hours a day will put an extra burden on the compressor. Here are some great preventative measures you can take to ensure your unit lives its best life.

Ventilation – a lack of ventilation can cause humidity to accumulate and not leave the room. You can improve your ventilation by covering cracks in windows and doors or filling them with sealant. These cracks will bring in unwanted moisture from the outside.

Leaky Pipes, and Roofs – Fixing any leaks in your home will help reduce any moisture from entering the environment. Leaky pipes can cause mould to grow, which can lead to respiratory issues as well as trigger asthma and allergies.

Avoid using heating appliances – Unvented natural gas, kerosene models, heaters will contribute to moisture in a room. Avoid using it or replace it with alternate electrical appliances.

Install Exhaust Fans – Places like the bathroom and kitchen acquire a lot of humidity. Cleaning yourself and cooking meals will add dampness to the area. Installing an exhaust fan in these rooms can help suck out the excess moisture in the air.

Regularly Emptying Water Tank – If the water tank is full, the dehumidifier will not function properly, and it could even damage the circuit board. Ensure you empty it regularly in order to run your dehumidifier efficiently.

Regularly Dusting – Cleaning the coils and air vents to make sure they are free from dust will make the unit more efficient while operating.



When should you use a dehumidifier?

You should use a dehumidifier if you notice any of these factors in your household.

  1. Moist or wet stains are present on the walls or ceiling.
  2. The room feels unpleasantly stuffy.
  3. Windows are covered with condensation.
  4. Musty odours exist.
  5. Mould is visible.
  6. Excess moisture.

Should I run my dehumidifier during the winter?

Running your dehumidifier during the winter is unnecessary since the air is typically dry during this time of the year. The dry air can cause dry skin, chapped lips, nose bleeds, runny noses and a whole bunch of other stuff.

Instead of using a dehumidifier during this time, you can replace your unit with a humidifier that puts moisture back into the air.

How quickly should a dehumidifier fill up?

It should take around 6-7 hours for your dehumidifier to fill up with water. However, this is a rough estimation as it can depend on your chosen model as well as how much moisture is in the air of your home.

How long do I need to use a dehumidifier after a leak?

It can take anywhere between a day or a week for a dehumidifier to be effective after a leak. A small leak in the corner of a room won’t take long, only about a day, but an actual flood of water is more likely to take closer to a week. It is all relative to the severity, so keep a close eye on the humidity levels and check the water tank several times per day.

What time of day to run a dehumidifier?

The best time of day to run a dehumidifier is between 10 pm, and 7 am. This is because it is prime time for condensation and moisture to make their way into the air of our home.

It’s also the best time for a dehumidifier for the bedroom, or any other room, to run as it’s cost-effective in that very few people have electronics running during these hours.

Should you run a dehumidifier with the windows open?

No, you should not run a dehumidifier with the windows open. This is because open windows let in the outside temperature and humidity, which can cause mould to grow.

Does a dehumidifier cool a room?

Dehumidifiers can help cool a room because it greatly reduces humidity which is the main cause of discomfort in a room. Humidity is that heavy muggy feeling you feel due to excess water vapor in the air.

Final Thoughts

Your room dehumidifier shouldn’t take more than 12 hours to work properly and knowing how much capacity your unit holds and the level of air quality will help determine how long you will need your dehumidifier running throughout the day.

Before you know it, you will be able to run your dehumidifier all day – keeping your home free from excess moisture and ensuring you have the best possible air quality all no matter the weather.

Last Updated on March 25, 2021 by Gemma Tyler Protection Status