Vicks Cool Moisture V3900 vs Vicks Filter-Free Ultrasonic V4600
In short: The Vicks Filter-Free Ultrasonic V4600 costs $10 less; the Vicks Cool Moisture V3900 genuinely holds a larger room (246 sq ft against 234 sq ft); the Vicks Cool Moisture V3900 cannot produce white dust on hard water and the other can; they are different mechanisms entirely — evaporative against ultrasonic; the Vicks Filter-Free Ultrasonic V4600 costs about $29 less a year in wicks and watts.
| Spec | Vicks Cool Moisture V3900 | Vicks Filter-Free Ultrasonic V4600 |
|---|---|---|
| Approx. price | ~$60 | ~$50 |
| Type | Evaporative | Ultrasonic |
| Mist | cool | cool |
| Rated output | 1 gal/day | 0.95 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 | 246 sq ft | 234 sq ft |
| Claimed coverage | 400 sq ft | Not stated |
| Claim vs physics | 1.63× | — |
| Tank size | 1 gal | 1.19 gal |
| Runtime at the claimed room | 15 hr | — |
| Real runtime at full output | — | — |
| Yearly running cost | ~$40 | ~$11 |
| Replaceable media | Wick, replaced through the season | None — nothing to buy |
| White dust risk | No | Yes |
| Humidistat | No | No |
| Noise on low | — | — |
| Top fill | No | No |
| Dishwasher-safe tank | No | No |
| App control | No | No |
| Power | 40 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
Vicks Cool Moisture V3900
- Solves the white-dust problem that drives most returns of the brand's ultrasonic models
- Keeps the VapoPad slot, which is usually why someone is buying Vicks in the first place
- Cheaper than the equivalent Honeywell evaporative while doing the same job
- Wick filters at roughly $14 every month or two, which the sticker price does not hint at
- No humidistat, though an evaporative slows itself as the room fills in a way an ultrasonic cannot
- Audible fan - it is the mechanism, not a fault
- The UV claim covers the water in the tank, not the air in the room, and Vicks words it carefully
Vicks Filter-Free Ultrasonic V4600
- One of the few units here that does not print a room-size figure it cannot support
- Very quiet - owners rank it among the quietest they have owned
- Dual pad slots give noticeably more menthol than the single-slot models
- White dust on hard water, and the VapoPad slots do nothing about minerals
- Bottom fill through a neck narrow enough that cleaning is a bottle-brush job
- Nothing senses the room - it mists at a set rate until the tank is dry