Dreo HM311S vs Dreo HM512S
In short: The Dreo HM311S costs $25 less; the Dreo HM311S genuinely holds a larger room (195 sq ft against 185 sq ft).
| Spec | Dreo HM311S | Dreo HM512S |
|---|---|---|
| Approx. price | ~$50 | ~$75 |
| Type | Ultrasonic | Ultrasonic |
| Mist | cool | cool |
| Rated output | 0.79 gal/day | 0.75 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 | 185 sq ft |
| Claimed coverage | 300 sq ft | 500 sq ft |
| Claim vs physics | 1.54× | 2.70× |
| Tank size | 1.06 gal | 1.32 gal |
| Runtime at the claimed room | 21 hr | 16 hr |
| Real runtime at full output | — | — |
| Yearly running cost | ~$33 | ~$33 |
| Replaceable media | Demineralisation cartridge | Demineralisation cartridge |
| White dust risk | No | No |
| Humidistat | Yes | Yes |
| Noise on low | 28 dB | 28 dB |
| Top fill | Yes | Yes |
| Dishwasher-safe tank | No | No |
| App control | Yes | Yes |
| Power | 30 W | 32 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
Dreo HM512S
- Same included-cartridge approach as the HM311S with a usefully larger tank
- Owners report two nights between fills at the settings they actually use
- Aroma tray sits outside the water path, so oils do not end up in the ultrasonic chamber
- Quiet enough for a nursery on its lowest setting
- The 500 sq ft figure implies about 16 hours of tank, which is a long way from the 42 on the listing
- Cartridges are a recurring cost and Dreo's stated interval is short
- Cool mist only, unlike the HM713S it otherwise closely resembles
- Some owners report the sensor reading high, which makes auto mode stop earlier than expected