How Much Can a Dehumidifier Lower Humidity?

High humidity is a common problem for homeowners. If left unattended for too long, too much moisture can lead to the growth of mold, mildew, dust mites, and other harmful organisms. This can trigger allergies, asthma attacks, and other health issues. It can also damage furniture and your house structure. To prevent the harmful effects of high humidity, residential dehumidifiers are used to maintain proper humidity levels in your home. 

The ideal setting for a dehumidifier is between 30% and 50% RH. Usually, the most comfortable level is around 45%, but if the room is extremely damp and cold, you can set the humidity lower or let the unit run continuously. However, in most cases, the continuous operation may be unnecessary and even dry up the air. 

When setting the relative humidity level, it’s also important to consider the ambient temperature. Whether you want to know how much water a dehumidifier can collect or how low it can decrease the humidity levels, we aim to answer your questions below.

How Much Moisture Can a Dehumidifier Remove in a Day?

Dehumidifiers work to remove moisture from the air using different methods. The two main types of dehumidifiers are called refrigerant and desiccant. 


The refrigerant or compressor dehumidifier is most common in residential spaces, especially in basements. It works similarly to an air conditioner as it uses a compressor to pump the refrigerant through the coils to facilitate the cooling system. 

The warm, moist air is drawn in by a fan and then passes through the cold metal coils. As the air cools down, the vapor condenses into water droplets. This is what your dehumidifier collects in its water tank. 

With the excess moisture removed, the dryer air is then released into the room. Portable refrigerant dehumidifiers today typically range from 20 to 50 pints in capacity. 

Refrigerant Process


A desiccant dehumidifier uses a type of chemical that binds with the water vapor in the air until the desiccant’s maximum extraction capacity is reached. Most desiccant dehumidifiers don’t have a tank that collects water. Some desiccants are disposable, which means it dissolves into the water it absorbs and must be disposed of after one use. If the desiccant is renewable, such as silica gel, it is simply reheated to dry out the moisture by plugging the unit into a power outlet. 

Full-sized desiccant models also use silica gel filled into a wheel that rotates inside the unit. Unlike other desiccant dehumidifiers, it includes a condenser and water tank. A portion of the dried air is heated and it absorbs the moisture from the saturated desiccant before condensing into water. The capacity is around 10 to 20 pints.


Another type of mini dehumidifier uses the Peltier effect or thermoelectric cooling technology. The main process is similar to a refrigerant dehumidifier in that it cools down the warm, moist air to draw out the water vapor. But rather than a compressor and evaporator coils, this mini dehumidifier uses a Peltier module with a heat sink on each side. 

As the air cools down on one side of the Peltier, water drips into the tank. Then, the dried air passes over the hot side and is released into the room. Its daily capacity is much smaller, typically 8 to 16 ounces for standard models, and up to 30 ounces for the largest models.

Optimal Humidity Setting for Dehumidifier

Control Humidity

The ideal range of relative humidity to maintain your comfort is from 30% to 50% RH. When the relative humidity drops below 30%, the dry air absorbs moisture from any moist surface, including your skin, nasal airways, and eyes. With low humidity, you may suffer itchy eyes, a dry and scratchy throat, and nasal congestion. 

On the other hand, when the relative humidity reaches above 50% RH, it can create a perfect environment for mold and mildew growth, which can then trigger allergies and even damage your belongings. So if your dehumidifier has a humidistat, choose a setting between 30% and 50% RH. Most people would be comfortable at a 45% setting, but the best for you depends on your individual preference and the ambient temperature.

The dehumidifier’s humidistat measures the humidity in the room and automatically adjusts it to maintain your preferred setting. Once you select your desired humidity level, the unit will dehumidify the room until the relative humidity is lower than your setting. When the humidity rises above your setting, the unit will resume dehumidifying the room. 

The ambient temperature must also be taken into account when choosing the right humidity level for your house. Cooler air can hold less moisture and thus, maybe more comfortable at a lower humidity level. If the outdoor temperature is between 20°F and 40°F, set the humidity no higher than 40%. If the temperature is between 10°F and 20°F, set the humidity no higher than 35%. And if the temperature is below 10°F, set the humidity at 30% and no higher. Note that most dehumidifiers will only work in low temperatures down to 41°F for refrigerant models, or 33°F for desiccant units.

How Low Can a Dehumidifier Go?

Dehumidifier Checked

When setting the humidity on your dehumidifier, it’s not always best to select the lowest humidity setting. Different types of dehumidifiers give you different options.

For instance, standard refrigerant dehumidifiers allow you to set the humidity level on the digital display. Then, the unit will automatically cycle on and off to maintain this setting. You can usually choose from 30% to 80% or 90% RH in 5% increments.

This type of dehumidifier usually also includes a Continuous function. The unit will run nonstop for 24 hours, which can be useful in large spaces with extreme humidity like a basement with a floor drain available. Although, note that in the continuous mode, the dehumidifier will keep working even when humidity is already below 30% RH, giving you excessively dry air.

Full-sized desiccant models are similar to small refrigerant dehumidifiers in both appearance and features. They also include an automatic humidistat and digital display so you can set your preferred humidity level from 30% to 80% RH and the unit will maintain it without your constant supervision

Mini Peltier or thermoelectric dehumidifiers are commonly used at home, particularly in small rooms. They don’t provide as much control over the humidity levels as the larger models do. A Peltier unit typically only includes one button so you can turn it on or off. However, there are a few newer large models with an additional humidistat that allows you to set the humidity level you want. 

How Much Water Should a Dehumidifier Collect in a Day?

Draining Options of a Dehumidifiers

How much water a dehumidifier collects in a day depends mostly on its daily capacity. A higher capacity means the unit can remove more moisture per day and thus will be able to collect more water. The pint ratings indicated are measured in a controlled environment. A 50-pint dehumidifier may not collect a total of 50 pints of moisture in one day if it’s not running continuously for 24 hours or the room is smaller than the recommended range.

It also doesn’t necessarily mean that the tank in a larger capacity dehumidifier will fill up before that in a smaller unit. Obviously, a larger tank can hold more moisture, and thus the unit can run for a longer period before filling up. A larger dehumidifier usually comes with a larger tank, but this isn’t always the case. In general, a smaller tank with the same dehumidifier capacity will fill up faster. 

Another important factor is the humidity levels in the room you’re dehumidifying. Higher humidity means there is more moisture the dehumidifier can collect. The room size also affects how much moisture your dehumidifier needs to remove. If you want the most accurate representation of the dehumidifier’s actual performance and energy costs, look for Energy Star ratings. Having an Energy Star certification guarantees high energy efficiency.


What is the best humidity setting for a dehumidifier?

There is no one ideal setting for a dehumidifier in all situations. The optimal relative humidity is between 30% and 50% and you can adjust the setting according to the temperature and your preference.

Do you need to run a dehumidifier constantly? 

There is no need to run a dehumidifier constantly. Ideally, it should only run when the relative humidity reaches above 50%. Continuous operation may be unnecessary and inefficient.

Does a dehumidifier cool a room? No, a dehumidifier does not produce cold air like an air conditioning unit. However, lower humidity can help you feel cooler and more comfortable. 

How long does it take for a dehumidifier to work?

Depending on the room size and condition, you can usually notice a change in humidity within a few hours of running a dehumidifier. When dehumidifying a basement for the first time, it can take six to 12 hours; for the whole house, it can even take a couple of days to get the humidity down to your preferred level.

How long does it take for a dehumidifier to fill up?

As mentioned, it depends on factors such as the dehumidifier capacity, tank size, and the room’s size and dampness. On average, a standard 50-pint unit may take about six to eight hours to fill the tank with water. It can take even shorter or longer for smaller models.

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