Dehumidifier vs. Humidifier – What is The Difference?

No matter where you live in the country, you’ve likely had problems with your home being either too damp or too dry. This amount of moisture in your home’s air is the Relative Humidity (RH). Ideally, it should be between 30-50% RH. If the air in your home is too dry, it has a low RH. On the other hand, the RH may be too high if it is very damp. 

Dehumidifiers and humidifiers are two HVAC devices you can use in your home to control its humidity to comfortable levels. To learn all the differences between dehumidifiers vs. humidifiers, their benefits, how they work, and when you need one for your home, continue reading this detailed guide!

dehumidifier vs humidifier

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What Is The Difference Between a Dehumidifier and a Humidifier?

The main difference between dehumidifiers and humidifiers is that humidifiers add moisture, while dehumidifiers remove moisture from the air in your home. 

Dehumidifiers take away moisture from the air when it is too humid. It collects the moisture in a reservoir, which you will routinely need to empty the water unless it is plumbed directly to a drain. Dehumidifiers are often used in the wet, sticky summer months to reduce hay fever and seasonal allergies

On the other hand, humidifiers add moisture into the air when it is too dry. Therefore, you will have to routinely add water to it unless it’s connected to your home’s water line. Usually, humidifiers are used in the dry winter months. 

Humidifier vs. Dehumidifier Quick Comparison

DeviceDehumidifierHumidifier
FunctionRemoves moisture from the airAdds moisture to the air
Necessary maintenanceEmpty water collection tank (unless connected to a drain)Add water to the reservoir tank (unless connected to a water line)
When to useWhen it’s warm and humid, usually in the summer monthsWhen it’s dry, typically in the winter months
How it helps occupantsReduces allergens and prevents mold and mildew growthKeeps skin from drying out, prevents chapped lips, reduces allergies and congestion

What is a Dehumidifier?

a small dehumidifier in the living room

A dehumidifier removes moisture from the air to reduce humidity levels. Dehumidifiers can lower your home’s air to 30 to 50% RH. Sometimes you just need a small dehumidifier for specific rooms in your home, such as the basement, laundry room, or bathroom. 

Benefits of a Dehumidifier

  • Lessens negative impacts of allergens 
  • Reduces asthma flare-ups
  • Prevents mold and mildew growth
  • Reduces musty and wet odors
  • Decreases pest infestations
  • Keeps laundry rooms, basements, and other areas at safe levels 

How a Dehumidifier Works

a diagram showing how a refrigerant dehumidifier works
  • A dehumidifier pulls air through cooled metal coils
  • Since cool air can’t hold as much moisture as warm air, water condenses from the air onto the coils
  • These condensed water droplets then drip into a collection tank\
  • It then blows the cooled air (now with less moisture content) back into your home with a fan. 

What is a Humidifier?

a humidifier releasing steam to the living room

A humidifier increases humidity by adding moisture into the air. It can be a standalone device that humidifies a single room (like your bedroom) or your entire home with a whole-house system that connects to your furnace. 

Benefits of a Humidifier

  • Helps with allergies and sinus irritation 
  • Improves congestions 
  • Help with sleep
  • Reduces static electricity 
  • Help with pet dander
  • Helps maintain wooden floors 

How a Humidifier Works

There are multiple humidifier designs to increase the RH in your home. They’re either heated or not: 

  • Cool-mist humidifiers circulate a cool mist with one of three methods
    • Ultrasonic: a disc submerged in water spins very fast, making water droplets form into a cool steam
    • Impeller: a small metal or ceramic impeller vibrates at high frequencies to transform liquid water into mist
    • Evaporators: air is blown across a wet filter or belt to transfer moisture to the air
  • Warm-mist humidifiers heat water until it’s boiling, producing steam that is cooled down before entering your room

Each type efficiently adds moisture to your room, and there isn’t much difference between the different methods in terms of functionality. However, you can add essential oils, inhalants, or other products to warm-mist humidifiers (steam vaporizers) to help with allergies or asthma. 

Related Article: Dehumidifiers vs Air Purifiers – What is the Difference?

When Should You Use a Humidifier or Dehumidifier?

humidity meter

The best time to use a humidifier is when your home is too dry. On the flip side, dehumidifiers are best to use when your home is too moist. Typically, the winter months are the driest, and your furnace further dries out the air. 

Summer months, especially during the rainy season, is typically the time of year with the highest humidity. In most cases, your central air conditioner will do an excellent job at maintaining the ideal indoor RH. However, you might need to supplement with a dehumidifier if the outside RH is too high. 

You’re probably wondering how you would even know if the RH in your home is too high or too low.

Here is how to quickly determine if your home is too humid or too dry:

  • Humidifiy when: (home is too dry)- you get shocked by static often, your lips are chapped, your skin is dry, and your eyes, nose, and throat are itchy
  • Dehumidify when: (home is too moist)- condensation on your windows, you feel hot and sticky, and/or you feel congested

Alternatively, some home thermostats measure RH, making your life much easier. Ideal levels are between 30-60% RH. If your thermostat does not indicate RH, you can purchase a simple digital hygrometer to measure it. 

Dehumdidier and Humidifier FAQs

The Essential Home & Garden team gets frequent questions about humidifiers and dehumidifiers; here are the top ones: 

Are humidifiers and dehumidifiers the same thing?

No, in fact, they are opposite things. Humidifiers increase humidity (add moisture) to your home; dehumidifiers decrease humidity (remove moisture) from your home. 

Can a humidifier be used as a dehumidifier?

No, a humidifier can’t be used as a dehumidifier. However, there are specific devices that are 2-in-1 devices that can dehumidify and humidify, but they are few and far between. 

Dehumidifier vs. humidifier for mold – Which is best?

Dehumidifiers are best for mold control. Mold reproduces in wet and moist environments, which indicates high humidity. Therefore, lowering the humidity will decrease the prevalence of mold.

To Humidify or Dehumidify

Humidifiers and dehumidifiers help control the relative humidity (RH) in your home. Humidifiers help add moisture to your home when it’s too dry. On the other hand, dehumidifiers remove moisture when there’s too much of it. Both help keep your home comfortable, reduce stuffiness, lessen allergies, and prevent the spread of mold.  

About The Author

Jonathon is a mechanical engineer with over ten years of experience in the HVAC industry. He has hands-on experience with all types of HVAC systems.

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