AprilAire 600M Whole-House Humidifier, Manual High Output Furnace Humidifier, Large Capacity Whole-House Humidifier for Homes up to 5,000 Sq. Ft., White

Why it's worth it

A bypass humidifier rated for homes up to 5,000 square feet and 17 gallons a day, with no blower of its own. It borrows airflow from the furnace to evaporate water off the pad, which keeps both the price and the installation simpler.

On paper the gap between this and the 700M is one gallon a day and 300 square feet. The real difference is runtime. In a cold climate where the furnace cycles all day, a bypass unit gets plenty of chances to evaporate water, and you'd have trouble telling the two apart. In a mild winter, or a tightly sealed house that rarely calls for heat, the fan-powered 700M pulls ahead.

This is the easiest unit here to put in yourself. There's no second fan to power, so you're dealing with a water line, a drain, and low-voltage wiring — that's it. It mounts on the return duct as well as the supply, which helps in awkward mechanical rooms. Owners replacing a decades-old humidifier often reuse the existing wiring, though most had to enlarge the duct opening to match the new footprint.

From our review of 8 whole-house humidifiers, by David Sinclair, Managing Editor

What we like

• +On paper the gap between this and the 700M is one gallon a day and 300 square feet
• +This is the easiest unit here to put in yourself
• +It's the one we'd hand a first-timer

What to know

• –Bypass means zero output when the blower is off
• –The control is manual, same as the 700M, so the seasonal dial-down is your job