Dreo HM311S vs Honeywell HUL535 Filter-Free Cool Mist
In short: The Dreo HM311S costs $5 less; the Honeywell HUL535 Filter-Free Cool Mist genuinely holds a larger room (246 sq ft against 195 sq ft); the Dreo HM311S cannot produce white dust on hard water and the other can; the Honeywell HUL535 Filter-Free Cool Mist costs about $22 less a year in wicks and watts; only the Dreo HM311S has a humidistat, so only it can stop when the room is where you asked.
| Spec | Dreo HM311S | Honeywell HUL535 Filter-Free Cool Mist |
|---|---|---|
| Approx. price | ~$50 | ~$55 |
| Type | Ultrasonic | Ultrasonic |
| Mist | cool | cool |
| Rated output | 0.79 gal/day | 1 gal/day |
| Output standard | Computed from the tank and the maker's longest runtime claim — the lowest setting | Computed from the tank and the maker's longest runtime claim — the lowest setting |
| Honest room size | 195 sq ft | 246 sq ft |
| Claimed coverage | 300 sq ft | 300 sq ft |
| Claim vs physics | 1.54× | 1.22× |
| Tank size | 1.06 gal | 1 gal |
| Runtime at the claimed room | 21 hr | 20 hr |
| Real runtime at full output | — | — |
| Yearly running cost | ~$33 | ~$11 |
| Replaceable media | Demineralisation cartridge | None — nothing to buy |
| White dust risk | No | Yes |
| Humidistat | Yes | No |
| Noise on low | 28 dB | — |
| Top fill | Yes | No |
| Dishwasher-safe tank | No | No |
| App control | Yes | No |
| Power | 30 W | 38 W |
Highlighted cells are the better number in that row, and only where a direction is unambiguous — more output and more supported room, less noise, cost and price. Honest room size and runtime are computed from each maker’s own published figures; here is the calculation.
Pros and cons
Dreo HM311S
- Ships with a demineralisation cartridge, which is the whole white-dust problem solved in the box rather than in a follow-up order
- Owners on hard water report no dust on dark furniture, which is the specific thing they bought it for
- Genuinely cheap for a unit with a real humidity sensor and app control
- Top filling and a tank shape wide enough to get a hand into for cleaning
- The cartridge is a recurring cost the sticker price hides - roughly $24 a year at Dreo's stated change interval
- TechGearLab's testing put its useful room size at closer to 200 sq ft than the 300 claimed
- No warm mist, so in a cold bedroom the mist is noticeably chilly
- The app is another account and another device on the network for what is a $50 appliance
Honeywell HUL535 Filter-Free Cool Mist
- No consumables at all - the only ongoing cost is electricity
- Runs a full 24 hours on a tank at a mist level that roughly matches its claimed room size, which is rare here
- Simple enough that there is very little to go wrong
- White dust on hard water, with no demineralisation option built in
- No humidistat, so it cannot stop itself over-humidifying a closed room
- Bottom-fill tank, so every refill is a trip to the sink carrying it upside down
- The ultrasonic disc scales in hard water and needs descaling to keep output up, which the manual covers but the box does not