Aprilaire 500 Bypass vs Aprilaire 600 Bypass
In short: The Aprilaire 500 Bypass costs $40 less; the Aprilaire 600 Bypass genuinely holds a larger room (4,188 sq ft against 2,956 sq ft); the Aprilaire 500 Bypass costs about $5 less a year in wicks and watts.
| Spec | Aprilaire 500 Bypass | Aprilaire 600 Bypass |
|---|---|---|
| Approx. price | ~$180 | ~$220 |
| Type | Whole-house | Whole-house |
| Mist | cool | cool |
| Rated output | 12 gal/day | 17 gal/day |
| Output standard | Maker's published output rate | Maker's published output rate |
| Honest room size | 2,956 sq ft | 4,188 sq ft |
| Claimed coverage | 3,600 sq ft | 5,000 sq ft |
| Claim vs physics | 1.22× | 1.19× |
| Tank size | Plumbed | Plumbed |
| Runtime at the claimed room | — | — |
| Real runtime at full output | — | — |
| Yearly running cost | ~$26 | ~$31 |
| Replaceable media | Filter, replaced through the season | Filter, replaced through the season |
| White dust risk | No | No |
| Humidistat | Yes | Yes |
| Noise on low | — | — |
| Top fill | No | No |
| Dishwasher-safe tank | No | No |
| App control | No | No |
| Power | 20 W | 20 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
Aprilaire 500 Bypass
- No tanks and no refilling - the failure mode that ends most portable humidifiers simply does not apply
- Twenty dollars a year in water panels is the cheapest consumable bill per gallon delivered in this catalog by a wide margin
- Humidity is distributed through the ductwork rather than pooling in one room
- Aprilaire publishing tight/average/loose coverage bands is a level of honesty no portable maker matches
- Nothing to clean weekly; the panel is swapped once a season
- It only humidifies while the furnace is running, so mild days leave the house dry
- Installation means a plumber or HVAC tech, a duct opening and a water line - typically $700 to $1,400 on top of the hardware
- A leaking or stuck solenoid valve puts water on the furnace, which is a failure mode portables cannot have
- No control over individual rooms - the whole house gets the same setting
- The 3,600 sq ft figure is the tight-construction number; an average home of that size needs the larger 600
Aprilaire 600 Bypass
- Seventeen gallons a day for $220 of hardware is the best capability-per-dollar in the entire catalog
- So widely installed that any HVAC tech can service it and parts are on every supply-house shelf
- Aprilaire states outright that the 5,000 sq ft figure is for tight construction and about 2,000-2,500 is realistic
- Twenty-five dollars a year and one panel swap is the whole maintenance burden
- Owners report decade-plus service lives with nothing but panel changes
- Humidifies only while the furnace runs, which on mild days is not often enough
- Installation typically $700-$1,400 on top of the hardware, and it needs a drain as well as a supply
- Bypass designs waste some water down the drain by design - it is not a closed loop
- Over-humidifying a cold-climate house condenses on windows and inside walls, and there is no per-room control to fix it
- Requires forced-air heating; useless with boilers, baseboards or minisplit heat