A dehumidifier does not replace air conditioning, but it can reduce the load on your AC unit

Your air conditioner already removes moisture from the air as it cools — that is part of how AC works. A dehumidifier removes moisture without cooling the room. If your AC is running constantly but the air still feels sticky, a dehumidifier can pull out extra water vapor and let your AC focus on temperature instead of fighting humidity. This means your AC compressor runs less often, which saves electricity and extends the life of the unit.

The catch: a dehumidifier uses its own electricity, so you are trading one energy cost for another. The real benefit shows up in specific situations — basements that stay cool but damp, rooms where AC struggles to reach, or climates where humidity stays high even after the temperature drops. In those cases, running a dehumidifier alongside AC is more efficient than cranking the AC higher to dry out the air.

If your AC is sized correctly for your space and your humidity levels are normal for your region, a dehumidifier is usually unnecessary. If you live in a humid climate, have a basement, or notice your AC running nonstop without the house feeling dry, a dehumidifier becomes a practical addition.

Key Takeaways

  • Air conditioners remove moisture as part of their cooling cycle, so a dehumidifier is not required for basic humidity control.
  • A dehumidifier reduces the work your AC has to do by pulling moisture from the air separately, which can lower electricity use if your AC is oversized or your space is unusually humid.
  • Running both a dehumidifier and AC uses more total electricity than either alone, so the setup only saves money if your AC would otherwise run constantly.
  • Basements, rooms far from AC vents, and humid climates are the most common situations where adding a dehumidifier makes sense.
  • If your AC keeps the house cool but the air feels damp, humidity is the problem — a dehumidifier will fix it faster than lowering the thermostat.

How air conditioning removes humidity

When refrigerant flows through your AC's evaporator coil, it gets very cold. Warm, humid air from your home passes over this coil and loses heat. As the air cools, the water vapor in it condenses into liquid droplets, the same way a cold glass of water gets beads on the outside on a hot day. That liquid drains out of your system through a condensate line, and drier air blows back into your home.

This process happens automatically whenever your AC runs. You do not have to do anything — the humidity removal is built in. On a typical day in a typical climate, this is enough. Your AC removes enough moisture to keep the house comfortable.

The system has limits. If the air outside is extremely humid, or if your AC is too small for the space, or if moisture is being added faster than the AC can remove it (like in a basement with a water table nearby), the AC cannot keep up. The house stays cool but feels clammy. That is when a dehumidifier becomes useful.

When a dehumidifier actually saves electricity

A dehumidifier uses between 300 and 700 watts, depending on the size and model. Your AC uses 3,000 to 5,000 watts when the compressor is running. If your AC is running constantly because it is trying to dry out the air as well as cool it, a dehumidifier can reduce how often the compressor kicks on. Fewer compressor cycles means lower total electricity use, even though you are running two machines.

This works only if your AC is oversized or your humidity problem is severe. If your AC runs 8 hours a day and a dehumidifier would run 12 hours a day to solve the humidity, you have not saved anything. But if your AC would run 16 hours a day without the dehumidifier, and the dehumidifier cuts that down to 8 hours, you come out ahead.

The other scenario is comfort: if your AC keeps the house at 72 degrees but it feels muggy, you might lower the thermostat to 68 to feel dry. That extra cooling costs money. A dehumidifier lets you keep the thermostat at 72 and still feel comfortable, which saves electricity without a dehumidifier running.

Basements and crawl spaces

Basements are the most common place where a dehumidifier makes sense. Basements stay cool naturally because they are below ground, but they are also close to soil and groundwater. Moisture seeps in through walls and floors, and the cool temperature means your AC does not run down there — so the AC cannot remove that moisture. A dehumidifier running in the basement pulls out the water vapor and prevents mold, musty smells, and damage to stored items.

Crawl spaces have the same problem. They are naturally damp and rarely reached by your home's AC system. A dehumidifier sized for the space and left running during humid months keeps the air dry enough to prevent rot in wooden joists and beams.

If your basement or crawl space has active water intrusion — water pooling on the floor or seeping up from below — a dehumidifier is a temporary fix only. You need to address the water source first. A dehumidifier cannot keep up with standing water or active leaks.

Rooms far from AC vents

Some homes have uneven cooling: bedrooms or corners of the house stay warm and humid while other rooms are cold. This usually means the AC ductwork does not reach those spaces well, or the thermostat is in a different zone. A dehumidifier in the problem room can dry out the air without requiring you to lower the whole-house thermostat and waste cooling in other rooms.

Before buying a dehumidifier, check whether your AC vents are blocked or closed. Furniture, curtains, or closed doors can stop cool air from reaching a room. Opening vents and doors often solves the problem without adding equipment.

Humid climates and seasons

In very humid regions — coastal areas, the Deep South, or the Pacific Northwest — outdoor humidity stays high even in cool weather. Your AC removes moisture, but the air coming in from outside is so wet that the AC has to work harder than it would in a drier climate. A dehumidifier can help, but the real solution is making sure your AC is sized for your climate. An undersized unit will never keep up, and adding a dehumidifier will not fix that.

Seasonal humidity is different. If your area is humid only in summer, running a dehumidifier during those months makes sense. If humidity is a year-round problem, you might be better off upgrading to a larger AC unit or installing a whole-home dehumidification system that works with your existing AC.

Dehumidifiers versus lowering the thermostat

If your house is cool but feels damp, you have two choices: lower the thermostat so the AC runs more and removes more moisture, or run a dehumidifier. Lowering the thermostat from 74 to 72 degrees uses significantly more electricity because the AC compressor runs longer and harder. A dehumidifier uses less total energy to achieve the same dryness.

The tradeoff is comfort. Some people prefer a cooler house and do not mind the higher electricity bill. Others prefer to keep the thermostat steady and use a dehumidifier. The math usually favors the dehumidifier if your humidity problem is moderate and your AC is already sized correctly.

Frequently Asked Questions

Will a dehumidifier cool my house?

No. A dehumidifier removes water from the air but does not lower the temperature. In fact, it produces a small amount of heat as a byproduct. If you need the house cooler, you need air conditioning. A dehumidifier only addresses humidity.

Can I use a dehumidifier instead of air conditioning?

Not in warm weather. A dehumidifier will not cool you down when it is hot outside. In cool but humid conditions — like a basement or a cool, damp room — a dehumidifier alone may be enough. But for typical summer cooling, you need AC.

Does running a dehumidifier and AC together cost more than running just AC?

Yes, if both are running at the same time. However, if a dehumidifier reduces how often your AC compressor cycles on, the total cost may be lower. This depends on how much humidity you are fighting and how oversized your AC is.

What size dehumidifier do I need?

Dehumidifiers are rated by how many pints of water they remove per day — typically 30 to 70 pints. A small bedroom needs a 30-pint unit; a basement needs 50 to 70 pints. Check the manufacturer's recommendations for your room size and current humidity level.

Will a dehumidifier help if my AC is broken?

A dehumidifier will make the air feel less sticky, but it will not cool the house. If your AC is broken, you need to repair or replace it. A dehumidifier is a supplement, not a replacement.