A dehumidifier removes moisture from the air, but it does not lower the room temperature—it actually raises it slightly.

A dehumidifier works by pulling humid air across cold coils inside the unit. The moisture condenses on those coils and drains away or collects in a tank. The air that comes back out is drier, but it has also been warmed by the dehumidifier's motor and compressor. The net effect is a room that feels more comfortable because the humidity is lower, but the actual air temperature stays the same or goes up by a degree or two.

This matters because many people buy a dehumidifier hoping it will cool their space, then feel disappointed when the room stays warm. A dehumidifier is not an air conditioner. If your goal is to lower the temperature, you need a different tool. If your goal is to stop the air from feeling sticky and damp, a dehumidifier does exactly that.

Key Takeaways

  • Dehumidifiers remove water from the air but produce heat as a byproduct, so room temperature stays the same or rises slightly.
  • Lower humidity makes a room feel cooler and more comfortable even though the actual temperature has not changed.
  • A dehumidifier and an air conditioner do different jobs: one dries the air, the other lowers the temperature.
  • The heat output from a dehumidifier is small enough that it rarely raises room temperature by more than one or two degrees.

Why a dehumidifier produces heat instead of cold

The cooling coils inside a dehumidifier are cold, but they are only one part of the machine. The compressor that powers those coils generates heat. The motor that runs the fan generates heat. All that heat stays inside the unit and warms the air before it leaves. The moisture that condenses also releases heat—a process called latent heat release. So even though the air passes over cold coils, the overall effect is that the air exits warmer than it entered.

An air conditioner works differently. It has two separate units: one inside your room that cools the air, and one outside that dumps the heat outdoors. A dehumidifier has only one unit, so all the heat it produces stays in your room. This is why running a dehumidifier in a small, sealed space can actually make the room warmer over time.

The difference between "feels cooler" and "actually cooler"

Humidity affects how your skin perceives temperature. When the air is very humid, sweat does not evaporate from your skin as easily, so you feel hotter than the thermometer says you are. When humidity drops, sweat evaporates faster, and you feel cooler even though the air temperature has not changed. This is why a dehumidifier can make a room feel noticeably more comfortable without lowering the temperature at all.

A room at 75 degrees and 70 percent humidity feels much warmer and stickier than a room at 75 degrees and 40 percent humidity. Running a dehumidifier in the first room will make it feel significantly better, but the thermometer will still read 75 degrees—or possibly 76 or 77 degrees, depending on the size of the unit and how long it has been running.

When to use a dehumidifier instead of air conditioning

A dehumidifier makes sense when humidity is your main problem, not heat. Basements, bathrooms, and laundry rooms often stay cool but feel damp. A dehumidifier will dry out the air and prevent mold and mildew without wasting energy on cooling air that is already cool enough. In spring and fall, when nights are cool but days are humid, a dehumidifier can solve the dampness problem without running an air conditioner all day.

A dehumidifier also costs less to run than an air conditioner. If you are trying to lower your energy bill and humidity is the issue, a dehumidifier is the better choice. However, if the room is genuinely hot and you need to lower the temperature, a dehumidifier will not help and may even make things slightly worse.

How much heat does a dehumidifier actually add

The amount of heat a dehumidifier produces depends on its size and how hard it is working. A small dehumidifier in a large room may raise the temperature by less than one degree. A large dehumidifier running constantly in a small, sealed room might raise the temperature by two or three degrees over several hours. In a room with normal air circulation and doors open to the rest of the house, the temperature rise is usually negligible.

The heat output is listed on the dehumidifier's specifications, usually in BTU (British thermal units). A 50-pint dehumidifier—a common size for basements—produces roughly 5,000 to 7,000 BTU of heat per hour. In a 1,000-square-foot basement with some air movement, this translates to a barely noticeable temperature increase. In a 100-square-foot bathroom with the door closed, it could be more noticeable.

Combining a dehumidifier with air conditioning

If a room is both hot and humid, you may need both tools. An air conditioner removes some moisture as it cools, but it does not remove as much as a dehumidifier can. Running a dehumidifier alongside an air conditioner allows the air conditioner to focus on temperature while the dehumidifier handles the remaining moisture. This combination is common in humid climates where summer air is both hot and sticky.

However, running both units at the same time uses more energy than running just an air conditioner. If you have a choice, an air conditioner alone is usually more efficient. A dehumidifier becomes worthwhile when the air conditioner is already running and the room is still too humid, or when you need to dry out a space that does not need cooling.

Signs your dehumidifier is working (and what to expect)

A working dehumidifier will collect water in its tank or drain line within a few hours, depending on how humid the room is. You will notice the air feels less sticky and smells fresher. Musty odors often fade as humidity drops. Condensation on windows and mirrors may decrease. These are all signs the dehumidifier is doing its job.

What you should not expect: a cooler room. If you are hoping the room temperature will drop, you will be disappointed. The dehumidifier is working correctly even if the thermometer does not move. If the room feels noticeably warmer after running the dehumidifier for hours, check that the unit is not too large for the space or that air is circulating out of the room—a sealed room with a large dehumidifier running constantly will warm up.

Frequently Asked Questions

Will a dehumidifier help if my room is hot and humid?

A dehumidifier will make the room feel more comfortable by removing moisture, but it will not lower the temperature and may raise it slightly. If the heat is the main problem, you need an air conditioner. If humidity is the main problem, a dehumidifier alone is enough.

Can I use a dehumidifier instead of air conditioning to save money?

Only if humidity, not heat, is your problem. A dehumidifier uses less energy than an air conditioner, but it does not cool the air. In a hot climate, you cannot replace air conditioning with a dehumidifier. In a cool, damp climate, a dehumidifier alone may be all you need.

Why does my room feel warmer after I turn on the dehumidifier?

The dehumidifier produces heat as it removes moisture. In a small, sealed room, this heat can accumulate and raise the temperature noticeably. Open a door or window to let warm air escape, or run the dehumidifier for shorter periods.

Should I run my dehumidifier and air conditioner at the same time?

You can, but it uses more energy than running the air conditioner alone. Air conditioners remove some moisture as they cool. Run both only if the air conditioner is already on and the room is still too humid.

What humidity level should I aim for?

Most people feel comfortable between 30 and 50 percent humidity. Below 30 percent, the air feels dry and can irritate skin and sinuses. Above 60 percent, mold and dust mites thrive. A dehumidifier with a built-in humidistat will automatically stop when it reaches your target level.