Aprilaire 700 review

Every sizing page on this site rests on one number - 296 square feet per gallon per day - and that number is derived from three of Aprilaire's published model pairs. This unit is one of them. So a review of the 700 is partly a review of our own foundation, and if its figures do not hold up, a good deal of this site does not either.

They hold up. Aprilaire publishes 18 gallons a day and up to 5,300 square feet for tightly constructed homes, and cites AHRI Guideline F - the residential humidifier sizing standard - as the basis. It is the only coverage claim in our set with a standard named behind it, and it is the reason this machine is the reference rather than the competition.

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Aprilaire 700 review - ranked, with the arithmetic

#	Product	Best for	Gal/day	Price
1	Aprilaire Model 700Top pickEighteen gallons a day against a stated 5,300 sq ft, cited to AHRI Guideline F. It is ducted, it needs installing, and it is the only sizing claim here with a standard behind it.	An actual whole house, sized against a standard	18.0published · 5,328 sq ft	$524.99 - Amazon#ad
2	Aprilaire Model 600Seventeen gallons a day to a stated 5,000 sq ft - the 700's capacity class in the 500's bypass body. It still borrows the furnace blower, so it humidifies only while that blower runs.	A large ducted house that still wants the bypass price	17.0published · 5,032 sq ft	$339.99 - Amazon#ad
3	Levoit Superior 6000SSix gallons, evaporative, and a Dry Mode that dries the wicks between runs. The 3,000 sq ft claim needs five times the output its own run time implies.	Mist-free humidification with a drying cycle	2.0implied · 592 sq ft	$249.99 - Amazon#ad

The claim, checked against itself

The wider point is what Aprilaire does not do. It does not print a tank capacity and let you infer a room size from it, because it has no tank. It does not give a square footage with no output figure to support it, which is the standard practice in the portable half of this market and the reason our gallons per day page exists. It states a rate, states a coverage, names the standard, and adds the qualifier that matters - *tightly constructed*.

Everything it publishes

What the fan actually buys

This is the whole reason the 700 costs more than the 600, and it is not capacity - the two are one published gallon a day apart, 18 against 17. What you are paying for is a fan of its own.

A bypass humidifier has no fan. It sits on the plenum with a duct running between supply and return and borrows the furnace blower to move air across the wet panel. That works well and costs less, with one consequence: it humidifies only while the blower is running. A fan-powered unit does not care what the furnace is doing.

• Mild weather is when this matters. In October and March the furnace cycles briefly and infrequently, which is exactly when a bypass unit gets the least run time - and the outdoor air is still dry.
• Modern high-efficiency heating makes it worse. Long, low-temperature cycles and variable-speed blowers change how much air actually crosses a bypass panel, and the humidifier's output follows.
• It also removes a physical constraint. A bypass unit needs somewhere to route a duct between supply and return. Some mechanical rooms simply have nowhere sensible, and the fan-powered unit does not need one.

If that trade is the decision you are actually making, it has its own page: bypass vs fan-powered works through where the line falls. If you have concluded you want ducted but not which kind, read that first and come back.

The drain is the feature

Almost everything this site publishes about humidifier maintenance is really about standing water. The EPA's every-third-day cleaning instruction, the pink film that is a bacterium rather than a mold, the mold prevention routine - all of it exists because a portable humidifier is a warm reservoir of still water in a dark plastic box.

This machine has no reservoir. Water enters from the supply, passes across the panel, and what is not evaporated goes down a drain. Aprilaire's own framing is that the built-in drain flushes mineral build-up. Nothing sits still long enough to grow a film, so the problem is not managed or reduced, it is absent.

That is the strongest single argument for the ducted category, and it is worth weighing against the fact that a portable is a fifty-dollar decision and this is not. It is also why the drainless Model 400 - which recirculates, and which Aprilaire puts on a twice-per-season panel schedule rather than annual - is a different proposition from this one despite publishing a similar capacity.

The maintenance figure that contradicts itself

Aprilaire's maintenance page puts Models 300, 500, 600, 700 and 720 on an annual Water Panel replacement, with an annual distribution tray inspection alongside it. The 700's own product page says once or twice per heating season.

Those are different instructions and we take the more specific document, which is the dedicated maintenance page. Either way the conclusion is unchanged and it is dramatic: one panel a year against a portable wick that Honeywell states should be replaced every 30 to 60 days. Across a 182-day heating season that is one purchase against three to six.

What it will cost you that a portable will not

This is not a purchase, it is a project, and every honest review of it has to lead with that.

• An installation. It mounts in ductwork. It needs a water supply, a drain, a 24 VAC transformer, a humidistat and an outdoor temperature sensor, and realistically a contractor - our whole-house installation cost page covers the break-even against running several portables.
• Ducted forced-air heating. If your house has baseboard, radiant or mini-splits, this machine is not an option at any price, and no ductwork is the page you want instead.
• Water down a drain. The property that keeps it clean also wastes water, continuously, all winter. A recirculating unit saves that water and gives up the benefit.
• Maintenance you cannot skip, on the EPA's advice about ducts. The EPA's position on duct cleaning states that moisture should not be present in ducts and that in-duct humidification equipment must be operated and maintained strictly as the manufacturer recommends. An annual panel is an easy schedule, and it is not an optional one - a neglected in-duct humidifier is a moisture problem inside your ductwork.
• No published warranty. Aprilaire states no warranty term on the product pages we read, which for a piece of equipment installed into a house is a genuine omission.

Who should buy it

• A house that needs more than about 17 gallons a day - roughly 5,000 square feet of circulated space, by our arithmetic or Aprilaire's, which agree.
• Anyone whose furnace cycles briefly, because that is the case where a bypass unit's dependence on the blower costs you real output.
• Anyone whose mechanical room has nowhere to route a bypass duct. This is a purely physical constraint and the fan solves it.
• Anyone who has given up on cleaning tanks. The drain removes the problem rather than easing it, and that is worth more over five years than any feature on a portable.

Who should not

• Anyone without ducted forced-air heating. Not a preference, a requirement.
• Anyone whose house needs 12 gallons a day or less. The Model 500 does that job as a bypass unit for less money, and capacity you cannot use is the commonest way to overspend here.
• Anyone buying it for the extra gallon over the 600. One published gallon a day is not the difference between these machines. The fan is.
• Anyone who needs it working this week. A portable ships and plugs in. This needs a contractor's calendar.

If ducted is out of reach but the capacity is the point, the third pick above is the honest fallback rather than a consolation prize: a large portable moves real water and needs no installation, and it brings back every tank-cleaning obligation this machine removes. That is the trade, stated plainly.