How Long Does It Take a Dehumidifier To Work?

Maintaining ideal indoor humidity between 30% to 50% RH is essential in keeping everyone’s health and comfort inside your home. When humidity levels hit 60% and above, the air can become uncomfortable to breathe. Prolonged exposure to excess humidity can even lead to health issues and damage to your furniture and house structure. To avoid any of these problems, a dehumidifier reduces the amount of moisture in the air. But it can take some time for the changes to be noticeable.

Usually, you can feel the dehumidifier’s impact on the humidity levels within a few hours of continuous operation. If you’re using it for the first time in a wet environment, you can wait 12 to 24 hours before the humidity reaches your desired level. Overall, the amount of time it takes for a dehumidifier to work depends on multiple factors such as the dehumidifier capacity and the size and condition of the space. We will talk about these factors in greater detail below.

How Long Does It Take For A Dehumidifier To Work?

The short answer is anywhere from a few hours up to a few weeks. Depending on its type, a dehumidifier starts working as soon as it is plugged in and turned on. However, you’ll notice a significant change in humidity after varying amounts of time.

When introducing a dehumidifier to a moderately humid room, say, 60% to 70% RH, it can take about six to 12 hours before the humidity level can reach between 40% and 50% RH. In some cases, it can take 24 to 48 hours of continuous use to get the humidity in the whole space down to the ideal range. 

For instance, if you’re using a high-capacity dehumidifier for the whole house for the first time, the unit may need to work continuously for up to two weeks. This is because it has more work to do to dry the air within the entire space along with organic materials like wooden furniture, fabrics, clothing, carpets, and hardwood floors. Once the moisture levels are reduced, the unit may cycle on and off to maintain your set humidity.

Turning on a Dehumidifier Constantly

How Does A Dehumidifier Work?

Based on the dehumidification process used, there are two main types of dehumidifiers: refrigerant and desiccant. In this article, we will only consider the refrigerant type. For more information on all types of dehumidifiers and how each of them works, you can learn about them here.

Refrigerant or compressor-based dehumidifiers are the most common type in households. A refrigerant dehumidifier relies on condensation to extract excess moisture from the air. It uses a compressor to pump the refrigerant to and from the condenser and evaporator coils. A fan pulls in humid, warm air and passes it over the cold coils where the moisture should condense. The water formed drips into a water tank or flows out through a drain hose. Once the moisture is extracted, the dryer air and warmer air is exhausted back in the room. 

This type of dehumidifier is most effective in warm and humid climates typically from 65°F and above. The air must be warm enough for the moisture to condense when cooled down. Otherwise, the condensate may freeze on the coils instead. 

Refrigeration Flow

What Factors Affect the Dehumidifier’s Performance?

The dehumidifier’s effectiveness in a given space depends on multiple factors, especially the unit’s capacity, the ambient humidity and temperature, and the room size.

Dehumidifier Capacity

This is the total amount of moisture the dehumidifier removes within a 24-hour cycle. For residential dehumidifiers, this is measured under the conditions set by the Department of Energy as of 2020, at 65°F and 80% RH. Thus, the standard dehumidifier capacities today are 20, 30, and 50 pints (or 22, 35, and 50 pints depending on the brand). 

A higher capacity means the unit can remove moisture at a faster rate in a larger room, but it can still vary per brand and model of the dehumidifier. For example, a 50-pint dehumidifier will be able to achieve your target humidity level compared to a 30-pint dehumidifier in the same room. However, it isn’t always a good idea to get the highest capacity dehumidifier you can find.

Humidity and Temperature

Another important factor that determines a dehumidifier’s performance is the level of dampness in the space it has to dehumidify. More moisture in the air means it has to work harder for a longer period to get the relative humidity level down to your setting. Naturally humid spaces such as the basement, garage, or laundry room will need a powerful dehumidifier. If there are visible signs of moisture like condensation on windows or spots of mold on walls, then you can expect the dehumidifier to have to work longer.

Furthermore, the ambient temperature can also affect the dehumidifier’s performance. A higher temperature allows the air to hold more water molecules. This is why dehumidifiers are most effective in warm and humid environments and dehumidifiers lose effectiveness as the weather gets colder. Using your dehumidifier in tandem with your air conditioner can also help increase both units’ performance during hot and humid days.

Room Size

Lastly, the room size also affects how long your dehumidifier needs to work to maintain optimal humidity levels. As you can expect, a dehumidifier will have to run for a longer time in a large room than in a smaller room with similar humidity levels. This is because it has to cover more ground and dehumidify a larger volume of moist air. Thus, whole-house dehumidifiers can take days up to weeks to remove enough moisture from the entire space.

Water Restoration Dehumidifier

How Do I Know If My Dehumidifier Is Working?

There are many signs that will tell you when your dehumidifier is not working properly. In most cases, you can easily find the problem and its appropriate solution by yourself. 

The simplest way to tell if a dehumidifier is working is if there are changes in relative humidity. You can check the humidity on the dehumidifier’s digital display if it has one and compare it with a separate hygrometer. If there are still no changes in the humidity after six hours, then either the humidistat or the unit’s cooling system is faulty.

To know if your dehumidifier is working, you should also check if it is collecting water. Dehumidifiers hold the moisture in a tank on the bottom half of the unit. If there are changes in humidity within a few hours of use, the tank must also have some water collected.

Compressor dehumidifiers naturally make a buzzing sound similar to air conditioners. But if you notice your unit is making unusual noises, then there is likely a problem with its compressor or another internal component. 

If you’ve been using the unit for three years or longer and you notice it’s not working as it usually would, there should be troubleshooting guides in your manual. If you can’t solve the problem yourself, it’s always best to have the unit checked by a professional.


How Quickly Should a Dehumidifier Fill Up?

The total volume of water a dehumidifier collects in a day also depends on its capacity, room size, and ambient humidity and temperature. On average, standard 20-pint dehumidifiers can collect about a gallon or two (8 to 16 pints) of water, while the largest (50 to 60-pint) can collect up to six gallons a day. The actual amount varies case by case. 

When the tank fills up, you need to empty it manually by removing the tank and dumping the water. During this time, the dehumidifier will not resume operation until the water is emptied and the tank is replaced. To avoid doing this multiple times a day, get a dehumidifier with a larger tank. Or better yet, use a dehumidifier with continuous draining options. Most modern dehumidifiers can be connected with a drain hose for automatic drainage via gravity. In this case, you don’t need to worry about whether your dehumidifier is working continuously even while you’re away.

Draining Options of a Dehumidifiers

Should a Dehumidifier Run All the Time?

A dehumidifier does not need to run constantly all the time. In general, you only need to run the unit when humidity levels hit 50% or higher. Remember that the optimal indoor humidity level is between 30% to 50% RH. Standard dehumidifiers have a humidistat that allows you to set the humidity from 30% to 80% and it will automatically cycle on and off to maintain this setting. 

Many portable dehumidifiers also include a Continuous mode where the unit runs nonstop for 24 hours or until the tank is full if you don’t have a drainage system set up. This is especially useful for large spaces with high humidity such as basements. However, the continuous operation may also waste energy when the unit runs unnecessarily. 

The best thing to do is set the humidistat to your ideal humidity level based on the ambient temperature. If the outdoor temperature is below 40°F, humidity must be not more than 40%. If the outdoor temperature is below 20°F, humidity must be not more than 35%. And if the temperature outside is below 10°F, humidity must be not more than 30%. 

How Long Does A Dehumidifier Last?

Most dehumidifiers will last five up to ten years if given proper care and maintenance. The unit’s overall performance and longevity can usually be seen in its build quality and manufacturer warranty. Always look for a trusted brand with a good warranty policy.

Ultimately, your dehumidifier’s lifespan depends on how well you take care of it. Simple maintenance steps you can do start with emptying and cleaning the tank as often as necessary. Keep the filters and air grilles clean to avoid dust buildup. The coils also need to be cleaned professionally. For more specific instructions, you can check your dehumidifier’s manual.


Dehumidifiers can take anywhere from a few hours up to weeks to maintain optimal humidity for the entire space it has to cover. The larger and more humid the space is, the more moisture your dehumidifier has to remove and the longer it has to work. Ideally, a dehumidifier should be shut off once it has achieved the set humidity level. If you want to save more on energy costs, choose an Energy Star certified dehumidifier with the right capacity you need for the room. For your convenience, get a unit with a built-in humidistat so the unit will turn off automatically. To avoid manual emptying of the water collected, you should also consider setting up a drain hose for continuous drainage.

Related Articles