Evaporative Vs. Ultrasonic Humidifiers

Evaporative or Ultrasonic? How to choose between these types of humidifiers

The difference between evaporative and ultrasonic humidifiers

I love a good vacation, don’t get me wrong, but my favorite place to be is in my comfortable and clean home. The problem is, even in my own house I could be breathing in bad air.

Indoor air pollution. Yep, that’s a thing.

While I am all for eliminating pollution in the outdoor atmosphere, I never even considered that I would need to maintain the air quality of my house. That’s why I now use a humidifier to help balance the amount of moisture in the air.

It is important for moisture to be in the air because it can help to prevent a lot of symptoms that are associated with dry, low quality air such as sinus infections, dry skin, and even damage to wood flooring and furniture.

Single-room humidifiers are the more popular option and in most cases, the less expensive option. There are two types of portable humidifiers, evaporative and ultrasonic. They both do a good job of adding moisture to the air in the room they are placed in, they operate quite differently.

Evaporative Humidifier

An evaporative humidifier works by evaporating the water inside and sending that water vapor into the air. There are some that evaporate using steam, known as warm mist humidifiers, and some that filter water and use a fan to blow cool air onto the filter in order to evaporate it. The most important function of the evaporative is that the evaporation happens inside the humidifier, so any substances that were in the water are left behind inside the tank.

Ultrasonic Humidifier

An ultrasonic humidifier uses a high-frequency, vibrating element to drive water into the air where they are then evaporated. They don’t actually heat water at any point in the process, which is why they may sometimes be called “cool mist” humidifiers.

When considering which type of humidifier is right for you, there are four ways that the two types differ and can help determine the one you will want to purchase.

  • Price
  • Noise
  • Mineral Deposits
  • Maintenance

Let’s look at how these qualities differ for each type.


The biggest difference in price for these two types of humidifiers, comes down to whether you want to pay more up front, or pay later for replacement parts. Initially, evaporative humidifiers are less expensive than ultrasonic humidifiers, although you will end up paying to replace filters every so often. The price will also of course depend on the quality of the product. You can always by a cheaper humidifier, but it may not last you quite as long.


You will typically find that ultrasonic humidifiers have a much lower sound output than evaporatives. This is because they don’t require the use of a fan. If you are putting the unit in an area that you don’t want to increase noise, then you should consider an ultrasonic. Alternatively, the evaporative will provide some white noise. One thing to keep in mind is that the high frequency of the ultrasonic vibrations may be too high for humans to hear, but it is possible that it is in the hearing range of your pets.

Mineral Deposits

Unlike evaporative humidifiers, ultrasonics vaporize the water droplets and whatever substances are in them. So, if you use hard water in your humidifier, you will see a grey dust that settles on the items surrounding your unit, and eventually gets inhaled by anyone that goes into that room. Because there is no filter used, there is nothing to trap the minerals. You can reduce the dust by using distilled water, but to avoid it all together, you are better off getting an evaporative humidifier.

Ultrasonic humidifiers can also be known to leave small puddles or damp areas nearby. This is due to the water droplets that are being propelled from the unit. You will typically see this if the humidifier is placed in a cold room that already has a high content of moisture. Placing your unit on a dresser or shelf will give the water droplets more time to evaporate, reducing the probability that this will occur.


Because evaporative humidifiers use a filter, they do require replacing, which is an operational cost. Besides replacing the filter, evaporative humidifiers require a lot less upkeep than ultrasonics.

The ultrasonic has no filter, however, because it does not heat the water to evaporate it, they are at a high risk of developing bacteria. Any bacteria that grows inside the unit, can be released into the air, reducing the quality of air. To prevent this, the humidifier needs to be disinfected and thoroughly cleaned frequently.

The EPA recommends cleaning the unit every third day of use. Make sure you are referring to the manufacturer's instructions on properly cleaning. You can also refer to our step by step guide on When and How to Clean Your Humidifier.

In Closing

If you despise frequent cleaning and maintenance, then you will be better off with an evaporative model. Whereas, if you refuse to buy and replace filters, you will want to choose the ultrasonic humidifier. As far as the price goes, you can probably find similar pricing for both types, just make sure that you are buying a good quality unit if you want results.

Resources— Guardian Technologies, AIHA, EPA, Humidifiers.com