Honeywell comparisons
HUL565 vs HUL588 vs HUL900: fill and humidity controls
Honeywell’s HUL565, HUL588 and HUL900 can all make visible ultrasonic cool mist, but their refill and humidity-control choices differ. Use the exact series manual rather than a similar name to decide whether you want inverted-tank filling, top access, approximate preset cycling or a numeric display.
Start with how you add water
The HUL565’s manual gives 1.5 gallons for tank and base reservoir combined. To refill it, lift the tank, turn it over and unscrew its cap. Its larger stated volume does not remove the lifting and inversion step. In contrast, the HUL588 is documented as top-fill; its tank can be replenished from above without turning it over. The Reflection HUL900 also offers top access, including a pitcher route described in its manual. If you are comparing these because you want to avoid carrying a full tank, that practical distinction may matter more than their similar visible-mist output. Compare the actual opening, spill path and emptying routine in each manual, not just a “wide tank opening” label.
Preset humidity cycling is not a numeric display
On the HUL565, a button selects one of four approximate humidity cutoffs—about 40%, 50%, 60% or 70% relative humidity—and the humidifier pauses at the chosen level. A separate three-level mist control adjusts output. The green reached indicator reports that the preset has been reached, but it is not a current-RH readout. A separate monitor is needed to see a room humidity number.
The HUL588 also has an electronic humidistat and indicator buttons, but its shared HUL585/HUL588 manual documents its own approximate preset behavior and top-fill format. It does not become a display-equipped model because it has status lights. HUL900 adds a numeric control display and a user-selected target, plus a built-in timer. It is the clearest option here when an on-device number and timer are essential, but its tank-capacity documents conflict: its manual says 1.2 gallons while current product/listing material says 1.4. Keep that uncertainty in mind if you need to meet a strict capacity minimum.
Do not assume every oil tray is the same as a diffuser
All three reviewed models document a separate aroma-pad route, not oil poured into the water. Their exact manuals warn against putting oils, medications or other additives in the tank or base. The HUL565 manual says its oil tray is not a diffuser and that oil evaporates separately from the water. If you require an essential oil to enter the water tank, do not rely on a generic Honeywell family label; check the exact model manual, because HUL530 documents a different permission and these models do not share that instruction.
Room fit and maintenance still need judgment
The manufacturer calls the HUL565 Large and the HUL588 Large; the numeric room-area statements found in retailer or search copy are not treated here as equivalent primary ratings. HUL900 is described as Medium by Honeywell. Do not convert those labels into square footage. If the room is unusually large, damp, open to other rooms or poorly separated, no category label guarantees a target humidity. Place the outlet away from walls and bedding, use a separate humidity monitor if you need a measurement, and turn the unit down if condensation appears.
These are ultrasonic products without a wick to replace, but they still need regular water care and cleaning. All three manuals call for fresh water and regular cleaning; follow each exact manual’s method, keep scale removal separate from disinfection where instructed, and do not submerge the electrical base. Hard water can leave mineral dust from visible mist, so distilled water or the maker’s optional demineralization cartridge may be worth considering. The HUL565 manual specifically allows an optional Protec PDC51V2 cartridge, sold separately.
A quick fit check
- Choose HUL565 when 1.5 gallons combined volume, inverted bottom-fill and four approximate automatic humidity presets fit your needs, and a live humidity display is not essential.
- Compare HUL588 when top-fill and indicator-button humidistat operation matter more than HUL565’s documented larger combined volume.
- Compare HUL900 when you want top access, a numeric control panel and a timer; do not treat its capacity as settled until the conflicting 1.2/1.4-gallon documentation is reconciled.
None of these decisions is a claim about measured noise, personal ownership or humidification performance in a particular room. They reflect the manuals’ operating differences. Read the full HUL565 assessment, HUL588 review and HUL900 review before deciding which limits you can accept.