Ultrasonic vs Evaporative Humidifier: Which is Better?

Ultrasonic and evaporative humidifiers are two of the most popular cool mist humidifiers (no heating element used in generating moisture). They both add humidity to the house although their working mechanisms, noise levels, sizes and maintenance routines differ. 

The main differences between ultrasonic and evaporative humidifiers are in the way they generate steam, their appearances, noise levels and maintenance routines. While ultrasonic humidifiers use sound vibrations to turn water into mist, evaporative humidifiers use a fan or rotating disk to speed up the natural evaporation of water. Both humidifier types are almost equally efficient at humidification. 

Ultrasonic vs Evaporative Humidifier: Similarities and Differences

The main comparison points between ultrasonic and evaporative humidifiers include the following:

Mode of Humidification

The first point of comparison between the Ultrasonic and Evaporative humidifiers is how they add humidity to the environment around them. Their individual humidification processes are as follows:

• Ultrasonic humidifier

Ultrasonic humidifiers produce mist by way of sound vibrations at a high frequency to add moisture to the room. This process is usually very quiet although not completely noiseless. You may hear the vibrations but the sound has such a high pitch that human ears can’t hear it. 

Given that the ultrasonic humidifier has no wick filter, it’s less costly and has fewer parts to maintain. 

• Evaporative humidifier

On the other hand, evaporative humidifiers work by blowing air over a wick filter to the room. The wick increases the surface area of the natural evaporation of water. Blowing air over the filter further increases the rate of evaporation thus adding most to the room. 

The fan used to blow air over the wick filter makes the evaporative humidifier a bit nosier than the ultrasonic humidifier. The noise, however, is barely noticeable. 

Size

In general, evaporative humidifiers are larger than the ultrasonic humidifiers for the same rating in terms of the floor space (in square feet) covered. However, they all come in compact sizes with some being very small to cover small areas such as desks and small rooms. 

The size of the humidifier mostly depends on the features it has. However, the evaporative ones will be slightly larger as they need to accommodate fans and filters. Both types of humidifiers will be larger when they have extras such as clocks, LED lights and large water tanks. 

The aim for any humidifier is to raise the humidity of the room to between 30% to 50%. Some humidifiers even come with their own hydrometers although you can purchase one if you need it. Hygrometers measure the level of humidity in the environment. 

Appearance 

In terms of appearance, ultrasonic humidifiers have a teardrop shape while the evaporative humidifiers have industrial designs. 

• Ultrasonic humidifier 

A majority of the ultrasonic humidifiers come in the shape of a teardrop with the mist coming out of the narrow top of the humidifier. This shape, although the most common for ultrasonic humidifiers, can be varied to accommodate fillable tanks, water bottle insertion points and other features. There are even small humidifiers that can be placed in a bowl of water to use it as the source of the mist. 

Given its artistic shape, it can also have clocks, lights and pads added to it then placed in a good location where it improves the aesthetics of the home. 

• Evaporative humidifier 

Evaporative humidifiers mostly adopt industrial designs as they have more parts to accommodate than their ultrasonic alternatives. They will have circular, square, rectangular and other more defined shapes to accommodate filters, filler tanks and the fans. Their designs also allow for ease of maintenance by making the replaceable parts more accessible. 

Maintenance

Ultrasonic humidifiers are easier to maintain compared to the evaporative ones. The differences in maintenance levels aren’t that drastic however. 

• Ultrasonic humidifiers 

Ultrasonic humidifiers produce a white or gray dust especially when the water used is hard or has some minerals in it. The reason for this is the lack of a filter (like it is in the evaporative humidifiers) to capture the minerals in the water.   

The sonic vibrations produced by the humidifier evaporates the water in tiny droplets which carry the minerals and other substances in them. As the water evaporates or settles on surfaces in the room, the mineral particles form some very fine dust particles on them. With time, this dust becomes notable and it can be quite hard getting rid of. 

These are some of the ultrasonic humidifier dangers as the dust can trigger allergies and other issues. Luckily, it takes a while for the dust to gather to large amounts. 

To mitigate this, you need to purchase ultrasonic humidifiers with ceramic cartridges which filter out the minerals. The cartridges are replaceable. This option, however, doesn’t completely do away with the dust. The other option is using water that has been purified through distillation by reverse osmosis or filtration to remove the minerals. 

Both solutions increase the cost of buying and maintaining the humidifier. 

• Evaporative humidifiers 

Thanks to the presence of a wick filter in evaporative humidifiers, the minerals in the water are trapped with very little gray or white dust being formed in the room. This makes evaporative humidifiers less demanding in terms of dusting the house.

Installation

Both types of humidifiers are very simple to install. Their installation procedures are also similar to each other. The main steps to follow when installing them are as follows:

1. Add the recommended amount of water into the humidifier’s reservoir tank. 
2. Plug in the humidifier. 
3. Position the humidifier at least 1 foot from any objects to prevent damage by moisture. 
4. Turn on the humidifier then adjust the settings accordingly. 

You can then replace any parts when needed. 

Noise Levels

Ultrasonic humidifiers are quieter than evaporative humidifiers due the ultrasonic ones not having a fan. The fan is the main source of noise in the evaporative humidifiers. The noise in an evaporative humidifier isn’t too much to bear as they’re only a few decibels and increase with the size of the humidifier. 

It should be noted that, while quieter than evaporative humidifiers, ultrasonic humidifiers still produce a low level of noise from the sonic vibrations. 

Lifespans 

Evaporative and ultrasonic humidifiers have similar lifespans which is about 5 years with good care. Eventually, they get mineral deposits and other issues which force you to replace them. 

Cost

There isn’t much difference in costs between evaporative and ultrasonic humidifiers although ultrasonic ones cost slightly more than evaporative humidifiers. The slight difference in the costs stems from the fact that ultrasonic humidifiers use technology that is relatively new and complex compared to that used in evaporative humidifiers. 

What you might save in the purchase of an evaporative humidifier may be what you spend on filters and other replaceable parts not needed in ultrasonic humidifiers. Essentially, they cost roughly about the same over the useful lifespans. 

Ultrasonic Humidifiers: The Good and the Bad

Pros

• Highly efficient in humidifying the house. 
• Quieter than evaporative humidifiers. 
• Little maintenance required. 
• You can add inhalants to use them for aromatherapy. 
• Safe as they have no hot surfaces or steam. 
• Smaller in size given fewer parts and minimal mechanisms. 

Cons 

• The dust generated makes surfaces dirty and can affect the dwellers of the house through allergic reactions to the dust in what’s called humidifier fever. 
• There are mineral deposits which accumulate inside them hence the need for cleaning. 
• The lack of heating allows bacteria to grow. 
• Costlier than alternative humidifiers. 
• Can make surfaces wet as they generate small droplets which may not evaporate by the time they fall back down. The thus need to be placed in specific locations.
• Needs demineralized water which increases the costs of operation. 

As long as you can use water that has no minerals, ultrasonic humidifiers are great. 

Evaporative Humidifiers: The Good and the Bad

Pros 

• Cheaper than ultrasonic humidifiers. 
• You can add inhalants to use with aromatherapy.
• No heating hence safe for the household. 
• Easy to clean and maintain. 

Cons 

• Can be infested with bacteria due to the lack of heat. 
• Has a fan hence generates some noise. 
• Accumulates mineral dust on its filters hence the need to replace them.

This type of humidifiers are more hands-on than their ultrasonic alternatives. 

Verdict: Which is the Better Humidifier?

Given that the humidifiers cost about the same, the choice is personal. 

You should go for an ultrasonic humidifier if you want a quiet humidifier that doesn’t have filters to change. You also get beautiful designs to choose from to add beauty to the house. You’ll incur slightly more. However, you’ll have to deal with dust every few weeks or months. 

You can go for an evaporative humidifier if you’d don’t mind the slight noise and the filter changes. They also create less dust in the house hence won’t need occasional dusting. 

Tim David

HVAC tech with over 30 years of experience. Retired and doing repair work on the side around Madison County, AL.