Dreo HM311 Review

For a humidifier with this price tag, we were impressed at every turn. There's not really a weak point to be found, and in a few cases, it tests on the upper end of our lineup. It's not the best option for many (or most) use cases, but for intermittent use, you could do a lot worse.

Humidification

We like the HM311 for small to medium-sized rooms, but the reality of this machine is it's just not powerful enough to reliably bring up and hold humidity evenly in larger rooms. That's not to say you won't find value with this unit if your bedroom or sunroom is on the larger side; at that point, it's more about proximity. On a nightstand next to a bed, or strategically placed near your more finicky tropical plants, should still do the trick.

This humidifier is in the 'Cool Mist' category, meaning vapor is created ultrasonically, so there are no hot steam concerns around little ones. This is by far the most common humidification technique on the market; it's cheap to run and reliable.

The humidity in our room increased by 9% in an hour (starting at about 40%), making a noticeable change. Bottom line, for a small and inexpensive unit, the HM311 does a good (not great) job of actually humidifying your space.

Ease of Cleaning

This is where the HM311 really shines. This is the absolute easiest unit to clean that we've tested.

The secret is that there are no corners for gunk to cling to. The tank is an oval with a wide, rounded bottom, and plenty of hand room clearance. It's as smart as it is simple, and we wish all brands would take note. Use as many fancy brushes and scrubbers as you want; some units have so many nooks and crannies that you never quite feel confident that there are no missed spots.

The base unit is similarly shaped. The only part that needs to be removed is the float valve in the tank, which pops out with a simple switch. Cleaning is less of a chore, and more like wiping down a plate after dinner. Which is great, because you'll want to clean this unit — and any humidifier! — every few runs. White dust (from normal water mineralization), pink slime, and other build-ups are an inevitable reality of these products.

Noise

The Dreo isn't especially loud, with an average running sound level at 41dB; about the same as a standard refrigerator with the compressor running. This is just about average for our tested lineup.

For what it's worth, it basically sounds like a light fan, and some of us didn't love that. It's not quite soothing white noise, but closer to a low whine which we think could be bothersome during sleep. On the other hand though, after running for a bit the condensation in the tank starts to drip, and some owners may actually prefer that faint dripping sound over other options.

Ease of Use

We're pretty happy with the usability of the HM311 all things considered. The tank capacity itself isn't too small compared with our tested lineup (4L, about a gallon), but it's small enough that you're not dealing with a lot of weight after a fill-up. But we do wish it had a handle. As it is, it can be a little awkward to carry and load onto the base. No dripping or spilling risk, though, which is nice.

Dreo landed on a nice compromise of tank capacity and output. While it's not especially powerful, limiting how much it can raise humidity in a short amount of time, it has a tested run time of a little over 43 hours on a single tank. That's well above average, and a big reason why we gave it our 'Best for Occasional Use' award. This is about as 'set it and forget it' as they come.

The controls are simple and effective. You've got buttons for Power, Ambient Lighting, Timer, and Power Level. There is no relative humidity sensor though, so you get what you get once it's running. If you do want an RH sensor to automatically control and keep a specific humidity level, plus a couple other smart features, you can choose to fork over another 10ish bucks and get the upgraded HM311S Smart version. Dreo does have an app available for either model, but it's really only needed for the HM311S.

Operating Cost

Estimating annual run costs is an interesting exercise; to learn more, take a look at our dedicated How We Test article. But the vast majority of the cost comes on the water treatment side of things, not electricity costs.

As mentioned, ultrasonic units use very little power. We estimate $9.29 in electricity for the average household, specifically for the HM311. That assumes running the unit for about 1/4 of the year. For a unit like this that may be used more sparingly, that could be even less.

Where you'll notice the costs are in purchasing distilled water, or de-mineralization treatment tablets, and we estimate this could be roughly $120/yr for the average household. We touched on this above, but whatever minerals are dissolved in your water are going to be vaporized with everything else. That goes into the air and into your lungs, and also results in a very fine white powder coating everything in your room over time. Hard water, soft water, filtered water… it doesn't matter. These minerals are smaller than a standard Britta filter removes.

Should You Buy the Dreo HM311?

It's no secret the HM311 doesn't score near the top in most categories, but that's not what you're buying it for. You're buying it for the sporadic need as it pops up through the year, and for that, you want something simple that you won't have to relearn or download the app that you deleted a few months back. This is your hero.

What Other Humidifier Should You Consider?