Diffuser vs Humidifier: What’s the Difference?

Diffuser vs Humidifier

Unless you want to increase the moisture level in a room naturally, most homeowners turn towards a humidifier. While they are effective, they aren’t the best option if you want to use essential oils for aromatherapy. In most cases, that device is a diffuser. While these systems have a lot in common, our diffuser vs. humidifier guide will explain the differences between these machines.


A humidifier is a device that turns water into moisture before dispersing it through the air. There are two main types of humidifiers, along with a handful of hybrid machines and variants. Below, we’re going to discuss what you should expect from each type of system.

Cool Mist Humidifiers

A cool mist humidifier has a water tank with a wick filter system that draws water into the machine. As air passes through the system with the use of an internal fan, moisturized air is released back into a room. Many cool mist humidifiers are ultrasonic as well. They are more expensive but quieter as ultrasonic humidifiers use vibration to create a fine mist instead of a wick and fan.

Warm Mist Humidifiers

These types of humidifiers function in a similar fashion, but the water inside is heated into steam and converted to a warming mist. Warm mist humidifiers are designed for smaller rooms, and are more expensive than a cool mist system. These systems are the closest thing to a vaporizer or diffuser, although there are some dual-purpose machines that can disperse your choice of warm or cool mist.


A diffuser can look like a humidifier, and it does produce a fine mist just like a cool or steam-based system. It’s not uncommon to find manufacturers that label their diffusers as humidifiers as well, but there is a distinct difference between these machines.

Diffusers are designed for aromatherapy, and allow you to diffuse essential oils. As water is turned into a mist, the oils are infused into the mist before being dispersed by the system. Most diffusers are in the ultrasonic class, and while they do produce moisture, they are not a replacement for a dedicated humidifier.

Coverage and Capacity

Aside from the fact that a diffuser is designed for essential oils, the biggest difference between these two systems comes down to coverage and capacity. You should be able to find these specifications on any humidifier or diffuser, and they have a major impact on how your machine will perform. It’s also an area where humidifiers have a clear advantage.

Humidifiers can cover a range of areas anywhere from a few hundred to several thousand square feet. Simply put, you can pick up a machine that can work with a cup of water or a whole house system that covers 6,000 square feet or more. The capacity on these systems can be between 16 ounces to more than 6 gallons, so the options are endless.

With diffusers, your options are limited to smaller areas. Most are sized to work in small to medium-sized rooms, which means they have smaller water tanks as well. You are unlikely to find anything over 1-gallon, although how much water a machine can hold doesn’t have anything to do with the output rate.


Both humidifiers and diffusers are easy to use and made to operate unattended. Runtime is tied to the output and capacity of these machines. Systems with a high output rate can produce a lot of moisture but could drain the tank dry in a matter of hours. Alternatively, just because a machine has a 2-gallon tank doesn’t mean it can run for 24 hours.

While runtime varies wildly from one system to the next, humidifiers provide homeowners with a longer runtime. Most can run for at least 8 – 24 hours, but there are a number of large systems that can run for several days. Diffusers are typically run at shorter intervals, but you should still pay attention to the runtime compared to its overall capacity.


This is one of the few areas we consider a tie in our diffuser vs. humidifier review. How easy either machine is to clean depends on how it was designed. A humidifier with a large opening or a top-fill system may seem easy to clean, but can you remove the water tank?

That can make a difference when it’s time to clean your machine, which may be quite frequently depending on the quality of your water. The same rules apply to diffusers as well. If it looks simple or has a relatively large water reservoir, don’t assume it’s easy to clean.


When it comes to features, you’ll have far more options with a humidifier than you will with a diffuser. That’s due in part to their size and the sheer volume of systems available. You can find humidifiers with digital displays, built-in timers, various modes, and variable speeds. Nightlights and reminders are common options as well.

While having more options at your disposal may seem to make humidifiers a winner when it comes to features, it all depends on what you’re looking for. We found far more diffusers with remote controls or Bluetooth connectivity. There are dozens of rechargeable models as well, and many have a similar set of features that are found on humidifiers.


There are two areas to focus on with safety regardless of whether you prefer a diffuser or humidifier. Any system that uses cool mist is going to be safer. If your home has rambunctious pets, a humidifier full of hot water isn’t necessarily a good idea. That’s why nursery humidifiers are designed to use cool mist, although most diffusers are cool mist systems as well.

Branding is also important with safety. Poor quality control can lead to a leaky system, which could cause someone to slip or damage furniture and flooring in your home. Given the number of small companies that produce these types of systems, it definitely pays to look before you leap – even if it’s a budget-friendly machine.


Normally pricing comes down to the type of features, branding, and the size of the system when you’re dealing with HVAC products. When shopping for a diffuser or humidifier, those factors do come into play, but even the most high-tech diffuser will usually be cheaper than a solid humidifier.

On average, you can expect to pay between $20 to $40 for a diffuser. By comparison, a humidifier can run anywhere from $25 to $200 depending on the size. Features are a large factor in pricing with both of these systems, but size plays a large part in the price point. Considering diffusers are smaller, they are also significantly cheaper.

The Verdict

As you can see, both a diffuser and humidifier can add moisture to a room, but humidifiers are the only option for dry areas over 300 square feet, in our opinion. While there are a few hybrid machines that can vaporize essential oils and produce enough moisture for larger areas, the options are limited.

If you need to humidify a large area or a system that runs continuously, a cool or warm mist humidifier is the best choice for your home, whereas a diffuser from a company like Pure Guardian or Stadler Form are the ideal options for aromatherapy and essential oils.

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