When to Use Dehumidifier with Air Conditioner

Dehumidifiers and air conditioners are both essential in maintaining indoor comfort. Air conditioners work to remove heat from a room, making the air feel cooler. Meanwhile, dehumidifiers reduce humidity by drawing out excess moisture from the air. While they work using similar processes, they are two different appliances with different purposes. However, using them both at the same time can be more beneficial for you.

During the summer, the heat is often made worse by high relative humidity, making it impossible to feel truly comfortable indoors. A dehumidifier and air conditioner working together control both the heat and humidity, helping you maintain the perfect indoor environment. You can use either of the two any time of the year, but you might be wondering when you should use both. 

If you want to know whether you need to use a dehumidifier, air conditioner, or both, which one you need, you must first understand what they do and how they work.

Dehumidifier vs Air Conditioner

Both dehumidifiers and air conditioning can impact the air temperature and relative humidity in a room. You may also notice some similarities in the parts and working process of an air conditioner and the most common type of dehumidifier. They can also produce similar effects in the room because of the changes in temperatures and humidity levels, but their main purposes are different.

A dehumidifier works to remove excess moisture and keep indoor humidity levels within the ideal range of 40% to 60% RH. As a result, this prevents the growth of mold, mildew, dust mites, and other potentially harmful organisms. With fewer of these airborne allergens, it reduces the risks of allergies, asthma attacks, and other respiratory problems. Proper humidity also protects your properties from damage due to moisture, mold, and pests. Additionally, dehumidifiers eliminate musty odors and help improve indoor air quality. 

On the other hand, the main function of an air conditioning unit is to remove heat from the air in the room and fill the space with cool air. It can also reduce humidity in the process, helping you feel more comfortable. The air conditioning system is especially needed during hot summer days. 

Dehumidifiers are typically portable and can be moved from room to room with no difficulty, while most air conditioners require more permanent installation. If your primary concern is the heat, then you may need an air conditioner more. But if you notice condensation and musty odors, then it’s highly likely that you need a dehumidifier.

How Does an Air Conditioner Work?

An air conditioner works using the same principle as a refrigerator and other appliances with a refrigerant system. It reduces the temperature inside by transferring the heat to the outside. An air conditioner consists of the condenser and evaporator coils, a compressor, a fan, and a coolant or refrigerant gas. The compressor pumps the refrigerant to the coils to facilitate the cooling process.

The warm air enters the cooling system through a fan and passes through a filter where dust, dirt, and other airborne impurities are trapped. Then, the air goes over the cold evaporator coils, where the liquid refrigerant evaporates into a gas. As the warm air blows over the evaporator coils, the coolant absorbs heat from the air, decompressing it into a warm gas. This produces cool air.

The cool air is released into the room while the warm air or the condensate is exhausted outside. Meanwhile, the warm refrigerant gas flows through the condenser coils where it’s compressed back into a liquid form as it releases the heat.

How Does an Air Conditioner Work

While the air cooling process is essentially the same, there are different types of air conditioners depending on the installation.  

The window type is probably the most common and the simplest to install. All you need is a window that is large enough to fit your AC unit. Wall air conditioners are almost the same as the window type except they are installed inside a wall with a sleeve. There are also portable air conditioners but usually with a smaller cooling capacity and less energy efficiency. They come with built-in wheels for easy transport and must be ducted out of a window. Split-type ACs are more efficient and quiet but are more expensive and difficult to install. Lastly, a central air conditioner distributes cool air to multiple rooms in your home, but it might be less efficient.

How a Dehumidifier Works

Dehumidifiers remove moisture from the air through different methods. The two main types of dehumidifiers are based on the moisture removal method they use, the refrigerant and desiccant. 


Most people are probably more familiar with the compressor or refrigerant dehumidifier. It works like an air conditioner as it uses a compressor to move the refrigerant along the coils to cool the air and remove moisture through condensation. 

A fan draws the warm, moist air into the unit and passes it over the cold coils. As the air cools down, it loses its hold on the vapor. Moisture condenses and drips down into a tank or flows out through a drain hose. Meanwhile, the dryer air is sent back to the room.

This type of dehumidifier generally performs well in warm and humid climates. It can only operate in temperatures as low as 41°F, or it will not be able to cool down the air until condensation. It is also at risk of frost forming on the coils, which could damage them irreparably. Standard refrigerant dehumidifiers available today can remove around to 50 pints of moisture per day.

Refrigerant Flow Chart


The desiccant dehumidifier uses a hygroscopic substance (usually calcium chloride or silica gel) that extracts moisture from the air until fully saturated. Desiccant dehumidifiers come in a variety of sizes, depending on the capacity and renewability of the desiccant used. 

There are disposable units that come in small containers filled with calcium chloride or a similar salt compound, and renewable ones with silica gel beads that need to be recharged every few weeks. Full-size units have a desiccant wheel filled with silica gel where the moisture is adsorbed. After it passes through the desiccant, dry air is pushed out into the room. The saturated part of the desiccant is heated so that moisture is removed and the desiccant is now reactivated to extract more moisture. 

Since desiccant dehumidifiers heat up the air before any condensation occurs, they can operate in lower temperatures and have lower risks of frost buildup. They are also quieter but usually more expensive and have a lower capacity than refrigerant units.

Desiccant Flow

Peltier Effect

Another method commonly used by mini dehumidifiers is called the Peltier effect or thermoelectric cooling technology. The process is similar to that of a refrigerant unit but on a much smaller scale. Instead of a compressor and coils, this dehumidifier consists of a Peltier module with a heat sink on each end. 

The humid air is drawn by a small fan through the cold side, and the moisture condenses into water, which drips into a tank below. The cold and dry air passes through the hot side which releases warm and dry air back into the room. 

Since a Peltier dehumidifier also needs to cool down the air to remove moisture, it can only work well in temperatures between 59°F and 86°F. Typically, it can only remove around 8 to 16 ounces or up to 30 ounces of moisture per day.

Peltier Effect Flow

When to use a dehumidifier and air conditioner simultaneously

A dehumidifier and air conditioner each have a different purpose but yield a few similar results. In particular, an air conditioner removes heat from the room while a dehumidifier reduces humidity.

To better understand the functions of these appliances, you need to understand the relationship between temperature and humidity. The relative humidity is the amount of water vapor in the air compared to the maximum amount it could hold at a given temperature. Although it does not directly affect the temperature (and vice versa), one can impact how we perceive the other.

When there’s heat and water, there will always be moisture in the air. However, hot air can hold more water. So if the temperature decreases while the amount of moisture remains the same, the relative humidity increases.

On the other hand, cold air is able to hold less water vapor. This is why the cold winter air is often very dry. In this case, there’s less need for both the air conditioner and dehumidifier. What you might need are a heater and humidifier.

Basically, you want to use a dehumidifier with air conditioner system running in the following situations:

  • It’s very hot and humid. Your dehumidifier will help the air feel cooler, which means your air conditioner won’t have to work quite as hard.
  • It’s mild temperature but still high humidity outside. In this situation, your air conditioner won’t be running constantly and may only come on for short periods during the day. That means your air conditioner won’t be pulling as much humidity out of the air during the cooling process. So running a dehumidifier during this periods can help keep the air from being too humid even when your AC isn’t running.

In many cases you can reduce how long it takes for a dehumidifier to work by teaming up your dehumidifier with your air conditioner.

Does a dehumidifier make a room cooler?

The short answer is no, dehumidifiers do not actually make a room cooler. As a matter of fact, the temperature of the air produced after dehumidification is a few degrees higher than the air inlet temperature. However, because of the change in relative humidity inside the room, the air can feel cooler to the occupants.

Hot air with more moisture simply feels hotter because your perspiration cannot evaporate. Sweat is produced to help cool your body, but when the air is already saturated with moisture, it cannot absorb your sweat fast enough. Thus, high humidity makes hot temperatures feel even hotter and the air feels heavy and sticky on your skin. So when a dehumidifier reduces humidity, the air feels cooler. You can amplify this effect by running a fan with a dehumidifier (with or without air conditioning).

Can an air conditioner dehumidify a room?

As the air conditioner removes heat from the room, it lowers the temperature and helps reduce the humidity as a result. You might notice your air conditioner producing condensate from the warm air. However, when it has to cool down air that’s heavy with moisture, the job becomes a lot harder, giving you lower efficiency and higher cooling bills. 

Meanwhile, the air conditioner cannot remove enough moisture at the same level that a dehumidifier can, creating an unevenly cold and clammy room. When the air is hot and not too humid, if the air conditioner is running almost constantly then an air conditioner alone may be enough to control the temperature and humidity.

Is It Cheaper to Run an AC or a Dehumidifier?

On initial purchase, window-type and portable air conditioners are usually more expensive than portable dehumidifiers. The actual cost can vary depending on the brand and size, not including the installation costs. Commercial portable air conditioners are the most effective for harder to cool spaces, but they are a bit more expensive and tend to be heavier and use more power.

Dehumidifiers have a few similar components, but they don’t need refrigerant systems as powerful as air conditioners to lower the temperature. 

And so, dehumidifiers generally consume less power, and running a dehumidifier alone costs less than running an air conditioner. However, you must still choose what you need most or you might end up spending more. 

Final Thoughts

You can use either a dehumidifier or air conditioner or both depending on your needs. If you live in a hot and dry environment, you need an air conditioner to cool the room. If you live in a humid region, then a dehumidifier may be more useful. But if you need to control both temperature and humidity to maintain indoor comfort, then you can benefit the most with the two working together.

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