Dreo HM311S vs Dreo HM512S
In short: The Dreo HM311S costs $20 less; the Dreo HM311S genuinely holds a larger room (195 sq ft against 185 sq ft).
| Spec | Dreo HM311S | Dreo HM512S |
|---|---|---|
| Approx. price | ~$50 | ~$70 |
| 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 | 300 sq ft |
| Claim vs physics | 1.54× | 1.62× |
| Tank size | 1.06 gal | 1.32 gal |
| Runtime at the claimed room | 21 hr | 26 hr |
| Real runtime at full output | — | — |
| Yearly running cost | ~$7 | ~$7 |
| Replaceable media | None — nothing to buy | None — nothing to buy |
| White dust risk | Yes | Yes |
| Humidistat | Yes | Yes |
| Noise on low | 28 dB | 28 dB |
| Top fill | Yes | Yes |
| Dishwasher-safe tank | No | No |
| App control | Yes | Yes |
| Power | 26 W | 26 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
- 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
- Takes a demineralisation cartridge for hard water, so the fix for white dust is an $18.99 accessory rather than a different humidifier
- Aroma pad tray outside the tank, so oils stay out of the ultrasonic chamber
- No demineralisation cartridge in the $49.99 box, so on hard tap water it leaves white dust until you buy one - roughly $24 a season at Dreo's change interval
- 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
- A litre more tank than the HM311S for $20 more
- 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
- Dreo's 300 sq ft rating is a modest stretch on its own tank and runtime figures, not a wild one
- The 300 sq ft figure implies about 26 hours of tank, against the 42 on the listing
- No demineralisation cartridge in the box; on hard water add a $25.99 three-pack, changed every two months
- Cool mist only, unlike the HM713S it otherwise closely resembles