Air Conditioner vs Dehumidifier: Which One Do You Need?

Summer is a great season to take a holiday. However, it’s also the season of scorching heat and oppressive humidity. Two of the most popular ways of dealing with heat and humidity are air conditioners and dehumidifiers. The technology that runs both is surprisingly similar, but the applications are leagues apart.

What is an Air Conditioner?

An air conditioner is a device that cools indoor air by removing heat and humidity from the space. It works using a refrigeration cycle, which involves a system of coils, refrigerant (coolant), and a compressor.

At the core of an air conditioner is the refrigerant, a chemical compound that circulates through a system of evaporator and condenser coils. Here’s how it works:

Inside the unit, warm indoor air is pulled in and passed over the evaporator coils, which contain the cold, low-pressure refrigerant. The refrigerant absorbs heat from the air, which causes it to evaporate and turn into a gas.
The compressor then pressurizes this gas, raising its temperature even further. This step prepares the refrigerant to release the absorbed heat.
The hot, pressurized gas is pushed through the condenser coils, usually located on the outside of the unit. Here, the heat is released into the outdoor air with the help of a fan, and the refrigerant cools down and turns back into a liquid.
The cooled liquid refrigerant returns to the evaporator coils to start the process over again.

This cooling process not only reduces air temperature but also removes moisture from the air. As the warm indoor air passes over the cold evaporator coils, water vapor condenses into liquid and is drained away — lowering the humidity in the room.

What is a Dehumidifier?

A dehumidifier is a device designed to remove excess moisture from the air, helping to reduce humidity levels in indoor spaces. While it shares some components and principles with an air conditioner—like coils, a refrigerant, and a compressor—its primary goal is not to cool the air, but to extract and collect water vapor.

Here’s how it works:

The dehumidifier pulls warm, humid air from the room into the unit using a fan.
This air is passed over cold evaporator coils filled with refrigerant. As the warm, moist air makes contact with the cold surface, the water vapor condenses into liquid droplets, similar to how moisture forms on a cold glass in a warm room.
The condensed water drips into a built-in collection tank or is drained away through a hose. This reduces the humidity level in the air.
The now drier (but slightly warmed) air is passed over condenser coils and released back into the room. Unlike an air conditioner, which releases cooled air, a dehumidifier typically returns air at a neutral or slightly higher temperature.

While the internal mechanics resemble those of an air conditioner, the airflow and purpose differ. A dehumidifier focuses on moisture control, which can help prevent mold growth, reduce allergens like dust mites, and create a more comfortable indoor environment—especially in damp basements or during humid seasons.

Key Differences Between Air Conditioners and Dehumidifiers

Category	Air Conditioner	Dehumidifier
Primary Function	Cools and dehumidifies indoor air by removing heat and moisture	Removes moisture from indoor air without significantly changing air temperature
Mechanism	Uses a refrigeration cycle: warm air is cooled via evaporator coils; heat is expelled outside	Also uses a refrigeration cycle: air is cooled to condense moisture, but heat is typically returned to the room
Heat Output	Expels heat outside via an exhaust or outdoor unit	Releases some heat back into the room, resulting in a slight warming effect
Air Temperature Effect	Lowers room temperature	Maintains or slightly increases room temperature
Humidity Reduction	Reduces humidity as a byproduct of cooling	Specifically designed to reduce humidity levels
Water Handling	Condensate is usually drained through a pipe or collected in a drip pan	Collected in a built-in tank or drained via a hose
Energy Use	Typically higher, especially for models that also heat or purify air	Generally lower, though it depends on humidity level and unit size
Fan Operation	Blows cold air into the room continuously or in cycles	Recirculates room air after moisture removal; may run more quietly
Portability	Available in portable, window, and split (wall-mounted) versions	Mostly portable units designed for specific rooms or spaces
Installation	Some types (e.g., split systems) require professional installation	Most are plug-and-play; no installation needed
Common Use Cases	Hot and humid climates; spaces that need cooling	Damp basements, laundry rooms, or homes with persistent moisture issues
Impact on Air Quality	Often includes filters to improve air quality; may include air purifiers	Removes moisture, which helps reduce mold, mildew, and allergens
Maintenance	Requires filter cleaning/replacement; some systems need professional servicing	Regularly empty water tank or check drain line; occasional filter cleaning
Noise Level	Varies by model; can be moderate to loud	Usually quieter than ACs but can vary depending on size and settings
Cost (Initial and Operating)	Higher upfront cost and power usage	Lower upfront cost and typically more energy-efficient for humidity control

Purpose

Dehumidifiers and air conditioners both use coolant and condenser coils. However, a dehumidifier uses changes in temperature to collect condensation, and an air conditioner uses the cooled air to lower the temperature in a room.

Humidity control

Both dehumidifiers and air conditioners lower the overall humidity in a room. However, a dehumidifier’s evaporator coil is designed to maximize condensation and collect it. When it comes to air conditioners, they have some impact on a room’s humidity. It’s mostly due to the fact that cooler air contains less humidity.

Impact on temperature

Air conditioners have a high impact on a room’s temperature, while dehumidifiers have a marginal impact. Dehumidifiers don’t typically vent the heated air away from the source. Thus, the air it expels is at a similar temperature.

Energy consumption

Under most circumstances, an air conditioner will use more energy than a dehumidifier. On average, a window air conditioner unit will consume three to seven kilowatt-hours. A dehumidifier of similar size uses about ten times less power.

Upfront and long-term cost

Based on the pricetag per unit, air conditioners and dehumidifiers have a similar cost. However, when you delve into the coverage area per cost, dehumidifiers are much cheaper. For example, a $200 dehumidifier will likely have an effective coverage of 3,000 square feet. While an air conditioner of similar cost will probably be able to cool an area of 300 square feet.

In terms of long-term costs, an air conditioner uses about 10 times as much power as a dehumidifier.

Size and placement needs

For complete coverage, you’ll probably need a window or portable air conditioner for each room or the rooms you spend the most time in. With dehumidifiers, you can usually get away with one per floor.

When to Use Each Appliance

Choosing between an air conditioner and a dehumidifier depends on the specific conditions of your space and what you’re trying to achieve—cooling, moisture control, or both.

Use a dehumidifier when:

Humidity is high but temperatures are mild: If your space feels damp or clammy but not particularly hot, a dehumidifier is more appropriate. It removes excess moisture from the air without cooling it, making the environment feel more comfortable and less sticky.
You’re trying to prevent mold, mildew, and musty odors: Basements, laundry rooms, crawl spaces, and poorly ventilated areas are prone to high humidity, which encourages mold growth and unpleasant odors. Dehumidifiers help maintain relative humidity below 50%, making these issues less likely.
You need long-term moisture control: In climates or seasons where high humidity is persistent (even if it’s not hot), a dehumidifier offers a more energy-efficient and sustainable solution than running an air conditioner solely for moisture removal.
You’re protecting sensitive materials: Excess humidity can damage wood furniture, electronics, books, and even musical instruments. Dehumidifiers are often used in storage areas or workshops to preserve these items.
You want to supplement an existing HVAC system: Central air systems often struggle to keep humidity in check in certain zones. A standalone dehumidifier can balance the moisture level in targeted areas without adjusting the whole system.

Use an air conditioner when:

Both temperature and humidity are high: If the air is hot and humid, an air conditioner is the better choice. It lowers the air temperature and simultaneously removes moisture, improving comfort on multiple levels.
You need rapid cooling for a single room: Portable and window air conditioners are excellent for spot cooling—ideal for bedrooms, home offices, or apartments where central AC isn’t available or efficient.
You want comfort during the hottest months: In summer, when heat buildup can affect sleep, productivity, and overall health, air conditioners provide fast, noticeable relief. They’re especially useful in upper floors or south-facing rooms that tend to overheat.
You need temperature control year-round: Some air conditioners (especially mini-split or HVAC systems) offer heating and cooling modes, giving you more comprehensive control over indoor conditions throughout the year.
You’re dealing with heat-sensitive occupants: In homes with babies, elderly residents, or pets, maintaining a consistently cool environment is critical. Air conditioners are better suited for this need than dehumidifiers.

In very hot and humid climates, you may benefit from using both appliances in tandem. For example, a dehumidifier can run during cooler, humid evenings or in basements, while an air conditioner handles daytime heat in living areas. Some high-end HVAC systems and portable units even combine both functions into a single appliance with separate humidity and temperature controls.

FAQ

Can a dehumidifier cool a room?

Typically, no. A dehumidifier can make a room feel more comfortable by lowering the humidity.

Can an air conditioner work as a dehumidifier?

Somewhat, but not effectively. Cooler air tends to be less humid. But an air conditioner does not remove excess moisture from the air.

Which is more energy efficient?

There are chemical dehumidifiers that use no electricity. Of those that use electricity, dehumidifiers consume about 10 times less energy than window or portable air conditioners.

Can I use both an air conditioner and a dehumidifier in the same room?

Yes, there’s nothing stopping you. One thing to consider is that since air conditioners have such a high power draw, you should make sure the breaker is rated to handle a dehumidifier and an air conditioner running at the same time.

Will a dehumidifier help with mold or musty smells?

Yes, a dehumidifier can help reduce mold and musty smells to a point. Mold and mildew thrive in a moist environment.

What if my dehumidifier is running but the room still feels damp?

There are several things you can do. If your dehumidifier runs on a sensor, you can manually turn it to a higher setting. Many models also allow you to install a drain pipe instead of using the collection bucket. Switching to the drain pipe will allow the unit to run continuously rather stopping in order to be emptied.