Smart humidity control: humidifiers and dehumidifiers

The target range

The EPA advises keeping indoor humidity below 60% relative humidity, ideally between 30% and 50%. ENERGY STAR gives the same 30%–50% as the optimum range for a building. Higher humidity makes mold growth more likely; very dry air is simply uncomfortable. The EPA also warns that condensation or moisture on windows, walls or pipes is a sign to act quickly to dry the surface and reduce the moisture source.

Measure before you buy

The EPA describes a humidity meter as a small, inexpensive instrument, about $10–$50, sold at many hardware stores. Put one in each problem area for a week: the basement, the bedroom, the bathroom after showers. Note readings in the morning and at night. A smart sensor can log this and send alerts, but a simple digital hygrometer is enough to decide.

• Basement or crawlspace above 60%: a dehumidifier is likely.
• Bedroom below 30% in winter: a humidifier may help comfort.
• Bathroom spikes after showers that last for hours: a fan or a humidity-triggered switch is the fix; see bathroom fan humidity switch.

Dehumidifiers: size, drain and cost

ENERGY STAR says certified dehumidifiers are 20% more efficient than non-certified models. Capacity is measured in pints of water removed per 24 hours. ENERGY STAR’s sizing guidance runs from about 20–30 pints per day for a slightly damp small to medium room up to 50 or more pints for a wet large space of over 2,000 sq ft. Frost forms on the coils below about 65°F, so a cool basement may need a unit made for low temperatures.

Continuous drain for a basement

A bucket that fills overnight makes a poor basement solution. Most portable units have a fitting that lets you attach a hose to drain continuously to a floor drain or sump. Check that the hose slopes downhill all the way, or choose a unit with a built-in condensate pump to lift water to a sink or a higher drain.

Running cost

A 450 W unit that runs 12 hours a day at 60% of full power uses about 1,180 kWh a year, roughly $210 at 18¢ per kWh (the EIA forecasts about 18.2¢ for 2026). Use our device energy cost calculator for your own unit and rate.

Smart control options

Before you put a dehumidifier on a smart plug, read the manual: many units reset to “off” after a power cut. Check the plug’s load rating against the appliance’s amps, and use an energy-monitoring plug such as those in smart plug energy monitoring to track real use.

Humidifiers: use them carefully

Humidifiers add moisture, so the EPA says not to humidify to indoor relative humidity levels above 50%. Its other points:

• Empty the tank, wipe it dry and refill portable humidifiers daily.
• Clean portable humidifiers every third day to reduce scale and microorganisms.
• Use water with low mineral content, such as distilled water, because ultrasonic and impeller humidifiers can send minerals in tap water into the air.
• Stop using the humidifier and contact your physician if you have respiratory symptoms you believe are linked to using it.

If windows fog or you see condensation, the setting is too high. Put a hygrometer across the room from the humidifier, not next to it.

Fix the source of moisture

An appliance treats the symptom. Check dryer vents, bath and kitchen fans, gutters and grading, and plumbing. A water sensor in the basement and under sinks catches leaks early; see our water leak protection kit. The EPA’s mold guide also says to dry wet items quickly and fix leaks promptly.