Dehumidifier vs Air Conditioner: Which One Fixes a Humid House?

Dehumidifier vs air conditioner at a glance

Based on PNNL's Building America Solution Center, ENERGY STAR and EPA guidance.

	Dehumidifier	Air conditioner
Main job	Remove moisture	Remove heat
Moisture removal	Whenever it runs, to the humidistat setting	Only while cooling; may not keep up in very humid conditions (PNNL)
Mild, humid days	Works	Removes no moisture if it is not cooling (PNNL)
Room temperature	Does not cool; adds a little heat from its motor and compressor	Cools
Basements	The usual fix	Basements are often cool enough that the AC rarely runs there
Efficiency label	ENERGY STAR IEF in L/kWh	ENERGY STAR cooling efficiency

Difference 1: how each removes water

Both use a cold coil: moist air passes over it, water condenses and drains away. An air conditioner's coil runs only when the thermostat calls for cooling, so it dehumidifies only then. A dehumidifier reheats the air after drying it and runs whenever humidity is above its setting. That is why PNNL lists stand-alone dehumidifiers, dehumidifiers integrated into the central system, and enhanced AC dehumidification as supplemental options when the AC alone cannot control humidity.

Difference 2: when the AC falls short

• Swing seasons. PNNL says AC removes no moisture when the air is humid but the temperature is at or below the set point, common in spring and fall.
• Very humid conditions. PNNL says AC may not keep up.
• Basements. They stay cool, so the thermostat upstairs rarely sends cold air there, yet ENERGY STAR describes basements as the setting DOE's dehumidifier test is designed around.

Difference 3: temperature

A dehumidifier does not cool. The electricity it uses ends up as heat in the room, so a dehumidifier in a closed room makes it slightly warmer. In a basement that is usually welcome; in a hot bedroom, the AC is the better tool, and once it is cooling it also removes moisture.

Difference 4: running cost

For moisture alone, a dehumidifier is the direct tool. ENERGY STAR estimates 515 kWh a year for the Midea Cube 50, about $88.58 at the EIA's 2025 US average of 17.2 cents per kWh, and 281 kWh for the smaller Most Efficient Levoit LDH-H251S. Running the AC colder just to dry the air cools spaces that may not need it. ENERGY STAR says certified dehumidifiers use about 20% less energy than conventional units.

Difference 5: the humidity target

EPA advises keeping indoor humidity below 60%, ideally 30 to 50%, and ENERGY STAR gives 30 to 50% as the optimum for dehumidifier settings. A dehumidifier lets you set a number; an air conditioner does not, unless it has a dedicated dry mode or the central system has integrated dehumidification. See the humidity level that prevents mold.

Which to use

Common situations.

Situation	Best tool
Damp, musty basement	Dehumidifier
Hot, humid upstairs in summer	Air conditioner
Mild but muggy spring or fall	Dehumidifier
Whole house stays above 60% even with the AC on	Both, or a dehumidifier integrated with the HVAC system
Laundry drying indoors	Dehumidifier, sized for wet conditions
Sealed crawlspace	Whole-home dehumidifier or conditioned air, per a contractor

Using both together

• Set the dehumidifier to about 45 to 50% and let the AC handle temperature.
• Keep doors and windows closed while either runs; ENERGY STAR says this helps a dehumidifier work efficiently.
• If the house stays humid with the AC running, ask an HVAC contractor about supplemental or integrated dehumidification, as PNNL describes.

For picks, see the best dehumidifiers, energy-efficient dehumidifiers and our sizing calculator.