Looking for an ultrasonic diffuser in 2016 has become more confusing than ever. This guide explains the features in budget diffusers and our top picks. I counted over 50 brands on Amazon and quite frankly I don’t recognize 90% of them and I have been writing about diffusers for quite a while now. Hmm. The silver lining for us as consumers though is that extreme competition has driven the price of ultrasonics lower than ever before. It is now very possible to get a basic ultrasonic, maybe even with a frill or two for less than dinner for two.
What features to look for in a budget diffuser
Auto-Shut off and Timers
Most budget diffusers will be pretty basic. Almost all have a safety feature where the diffuser will turn off automatically when the water runs dry. Most lower end models will not have a timer feature. This is one feature that I personally look for as essential oils are best used in moderation. I never run my ultrasonic diffusers more than 30 minutes at a time, and my nebulizer for even less per session. Having a diffuser that can automatically run on an interval is a perk. In our chart below, only the SpaRoom UltraMist has an intermittent setting.
Coverage and Output
The other important feature to consider is room coverage. Budget ultrasonics are likely to cover the space of a small room and not much more.
There are two main factors in room coverage: capacity and output level. The capacity is determined by the water reservoir size. Most smaller units hold 1/2 cup (125 ml) or less of water and about 5 drops of essential oils. Output level is how strongly a diffuser puts out mist. This is usually not something that can be controlled on a simple unit. For output control, look to the pricier H2E0.
Output level corresponds more to how large of a room can be covered, while output + water capacity will correspond to continuous run time. How strongly it mists and how much water in the tank will determine how long it can run before it is empty. As you can see when you compare models in the table below, most smaller units cover around 200-300 sq. ft. of space and run for a few hours. In the table below, the GreenAir Serenity has the longest run time at up to 8 hours.
So, in a budget model expect to find smaller reservoirs, smaller coverage areas, and run times around 3-4 hours. Do not expect to have much control over the settings other than on/off.