How Dehumidifiers Work | Live Science

If you’re considering buying a dehumidifier, you might be wondering “how do dehumidifiers work?” While the best humidifiers Add moisture to the air when it’s too dry, dehumidifiers remove moisture from the air when it’s too humid, making these little beauties ideal if you live in a hot climate or if you just want a more comfortable living environment in spring and summer.

We have all experienced humidity of one degree or another. This feeling of weight in the air usually comes from heat, rain or fog and can really affect how we feel during the day. When this happens, it can feel stuffy and even smell musty, which can lead to a host of problems for you and your home. This is where using a good dehumidifier comes in, and it’s worth learning and exploring how a dehumidifier can benefit you.

In this article, we will discuss what dehumidifiers are and answer a common question, how do dehumidifiers work? We’ll go over the benefits of using a dehumidifier and finally we’ll also give you an idea of ​​how much energy is needed to run these units and what it might cost you.

How do dehumidifiers work?

According to National Asthma Board, dehumidifiers change the humidity level of a room to 30-50% relative humidity by removing excess moisture from the air. When this happens, molds, dust mites and other allergens are less likely to survive.

A dehumidistat senses the humidity level in the air and turns the unit on when needed.

Refrigerant-based dehumidifiers are the most popular style of dehumidifier. They are generally composed of four parts:

  1. fan compressor which expands and contracts a refrigerant gas (like freon) to cool the coils
  2. heater which recovers the heat generated by the cooling process
  3. Refrigerated or cooled coils which absorb moisture from the air by condensation
  4. Collection tank or tray which collects moisture from cooled coils

Like a vacuum cleaner using a fan, dehumidifiers move air over their refrigerated coils. This process is similar to the operation of an air conditioning unit and causes moisture to condense on the coils of the unit. The warm air contracts and loses the moisture it can no longer hold as it moves through the cold coils. This is when it creates condensation, which accumulates inside the dehumidifier’s storage tank or bin. Then, through its other side, the dehumidifier sends the air back into the room via a heated coil.

Do dehumidifiers really work?

Dehumidifiers can provide the following benefits:

  • Improved air quality with reduced humidity
  • Mold prevention
  • Dusting
  • Personal comfort
  • Reduced energy costs
  • Protecting your home

For those of you wondering’do dehumidifiers help with allergies?‘, The answer is yes. By reducing the humidity in your home, you can also help reduce asthma symptoms and irritation. If you’re considering investing in a dehumidifier, you want to make sure you get all the benefits it has to offer. The good news is that there is a way to find out if a dehumidifier is really working for you.

Close-up of a dehumidifier in the living room with a woman and a cat on a sofa behind

(Image credit: Getty Images)

Measuring the efficiency of a dehumidifier

According to Code of Federal Regulations of the United States of Americathere are two things that tell how well and how well a dehumidifier works.

  1. Efficiency. You’ll need to rate a dehumidifier’s efficiency (its “energy factor”) to know if it’s working well for you. Find this by dividing the amount of water it removes by the amount of energy it consumes. This value is measured in liters or pints per kilowatt hour (L/kWh).
  2. Water removed per day. The amount of water a dehumidifier removes over a 24-hour period of continuous use (in liters or pints) is a clear indicator of how well the unit is working. Larger dehumidifiers, of course, remove more water than their smaller counterparts.

Power is also important to consider. Although it doesn’t indicate how good a dehumidifier is, higher wattage generally means it works harder and removes more water each hour. For example:

  • A small tabletop unit requires about 20 watts to operate, draws about 0.25 liters of water per day and has a reservoir of about 500ml.
  • A large dehumidifier removes about 50 liters of water per day and uses about 1000 watts.

However, you need to consider these numbers together and then compare the two units to assess their merit – horsepower alone can’t give you that.

The small unit will take approximately four days to withdraw one liter or 200 days to withdraw 50 liters, which will consume approximately 96 kWh (200 days x 24 hours x 0.02 kW). The large unit will take around a day to remove 50 litres, which will consume around 24 kWh. So in this example, the large unit is four times more efficient and 200 times faster than its small counterpart.

Find the right dehumidifier

As with any type of product, some dehumidifiers work well and do what they say they will do, while others leave a lot to be desired. There are some essential things you can do when shopping for a dehumidifier.

First, talk to the sales staff of the retailers that sell the units – you’ll likely get a more objective opinion from those not affiliated with a specific manufacturer. You can also find out about the return policies of the models you are interested in. That way, you can eventually take them home, try them out to see if they do what they claim, and if not, return them.

Finally, seek out and evaluate credible reviews, while paying close attention to what users are saying about the features most important to you.

Close up of dehumidifier next to sofa

(Image credit: Getty Images)

Do dehumidifiers consume a lot of electricity?

With all the benefits offered by dehumidifiers, energy efficiency is not one of them. Although they do not consume as much energy as an air conditioner which can be 300 kWh per month, they consume more than a standard refrigerator. Of course, like any appliance, the amount of energy a dehumidifier requires varies by type, size, and model. They consume on average about 280 watts (for comparison, computers usually use about 360 watts).

To save energy and money on your bill each month, find dehumidifier models that meet or exceed Star Energy terms. The higher a model’s Energy Factor (EF) number, the more water it draws per kWh of electricity it consumes. And, the larger the unit, the greater the impact on energy consumption and the cost of a higher efficiency rating will be.

Here is an example of Learn the metrics how much it might cost you to run an energy-efficient dehumidifier (EF of 2.0) versus an inefficient dehumidifier (EF of 1.0) in your home. In this case, assume a cost of 13 cents per kWh, with both units holding 70 pints and operating for 1,000 hours. The efficient EF 2.0 unit would cost about $90 per year to operate, while the inefficient EF 1.0 unit would cost about twice as much.

Making sure you clean and maintain your dehumidifier properly can also help you save on energy costs. Check out our guide for How to clean a dehumidifier for more information. And, if you’re hoping to save energy overall, using a home dehumidifier has a nice side effect: you can feel cooler and, as a result, reduce your energy use and your costs. This is because we tend to feel warmer in higher humidity. So when your space is less humid, you may not feel the need for fans or air conditioning as often.


The Code of Federal Regulations of the United States of America. (2007, January 1). Google books.

STAR ENERGY. (2022). The simple choice for energy efficiency.

Heffernan, T. (2022, April 29). The best dehumidifiers. Wirecutter: Reviews for the real world.

L. (2021, August 12). Energy efficiency of dehumidifiers: do dehumidifiers consume a lot of electricity? LearnMetrics.

The National Asthma Council Australia. (2016, February 16). National Asthma Board Australia. Retrieved April 29, 2022, from