A dehumidifier is not an air conditioner, though both remove moisture from air
A dehumidifier removes water vapor from the air but does not cool the room. An air conditioner cools the air and removes some moisture as a side effect. The two machines work on different principles and solve different problems. If your room is humid but the temperature is comfortable, a dehumidifier is what you need. If the room is hot, an air conditioner will cool it — and will also lower humidity as it does.
The confusion exists because both machines pull moisture out of air. But a dehumidifier releases that moisture as water in a tank or drain line, then pushes the same air back into the room at roughly the same temperature. An air conditioner cools the air first, which causes moisture to condense out, then sends the cooled air back into the room. One removes humidity; the other removes heat and humidity together.
Key Takeaways
- A dehumidifier removes moisture but does not lower room temperature, while an air conditioner cools the room and removes moisture as part of that cooling process.
- Dehumidifiers work by pulling humid air over cold coils, collecting the water that condenses, and returning dry air to the room at the original temperature.
- Air conditioners use refrigerant to absorb heat from indoor air and release it outside, which also removes moisture but is not their primary job.
- Running a dehumidifier in a cool room wastes energy; running an air conditioner when you only need to remove humidity also wastes energy and money.
- A dehumidifier costs between $150 and $500 to buy, while a window or portable air conditioner typically costs $200 to $600.
How a dehumidifier removes moisture without cooling
A dehumidifier pulls humid air into the machine and passes it over cold evaporator coils. The air cools as it touches the coils, and water vapor condenses into liquid droplets — the same way water beads up on a cold glass. Those droplets collect in a tank or drain into a hose. The now-dry air passes over warm condenser coils inside the machine, which heats it back up to close to its original temperature, then blows it back into the room.
The result is that the room stays at the same temperature but the air becomes drier. A dehumidifier uses electricity to run the compressor and fan, but it does not add cooling power to the room. In fact, because the machine generates heat as it operates, a dehumidifier can raise room temperature slightly — usually by 1 to 3 degrees Fahrenheit. This is why running a dehumidifier in an already-cool room is inefficient; you are paying to remove moisture while the air conditioner works against you by cooling the air back down.
How an air conditioner removes both heat and moisture
An air conditioner cools the room by circulating refrigerant through indoor and outdoor coils. The indoor coils absorb heat from the room's air, and the outdoor unit releases that heat outside. As the indoor air cools, moisture condenses on those same coils — the same process that happens in a dehumidifier. That water drains away, and the cooled, drier air blows back into the room.
The key difference is that cooling is the primary job. Moisture removal is a side effect. A window air conditioner or portable unit will lower humidity, but not as aggressively as a dehumidifier designed specifically for that task. If your room is 78 degrees and 70 percent humidity, an air conditioner will bring both numbers down. If your room is 72 degrees and 70 percent humidity, an air conditioner will cool it to 68 degrees to solve a problem you do not have.
When to use each machine
Use a dehumidifier if the room temperature is comfortable but the air feels damp, sticky, or smells musty. Basements, bathrooms after showers, and laundry rooms are common places where humidity lingers even though the temperature is fine. A dehumidifier will dry out the air without making the room colder. Humidity above 50 percent can encourage mold and dust mites; a dehumidifier brings it down to 30 to 50 percent, which is the healthy range.
Use an air conditioner if the room is hot. It will cool the space and remove humidity at the same time. A window unit or portable air conditioner works well for a single room. Central air conditioning cools the whole house and also controls humidity throughout. If you live in a climate where summers are hot and humid, an air conditioner is the right tool. If you live somewhere cool but damp — or if you have a basement that stays cool but wet — a dehumidifier is more efficient.
Some people use both. A basement might stay 65 degrees year-round but hold 80 percent humidity. Running an air conditioner there would waste money cooling air that is already cool. A dehumidifier solves the actual problem. In summer, a bedroom might be 76 degrees and humid; an air conditioner cools it to 72 and dries it out. In winter, the same room might be 68 degrees but humid from a bathroom or kitchen; a dehumidifier handles that without cooling further.
Energy cost and operating expense
A dehumidifier uses 300 to 700 watts, depending on size and how hard it works. Running one continuously costs roughly $15 to $35 per month in electricity, depending on your local rates. A window air conditioner uses 500 to 1,500 watts and costs $20 to $50 per month to run continuously. A portable air conditioner uses similar power. Central air conditioning costs more but spreads the load across the whole house.
The waste comes from running the wrong machine for the job. A dehumidifier in a room that is already cool will heat the room slightly while removing moisture, forcing the air conditioner to work harder. An air conditioner in a room that is already cool will waste energy cooling air that does not need cooling. Matching the tool to the problem — humidity alone, or heat and humidity together — saves money over the course of a season.
Dehumidifier and air conditioner features to compare
| Feature | Dehumidifier | Air Conditioner |
|---|---|---|
| Primary function | Remove moisture | Cool the room |
| Effect on temperature | Slight increase (1–3°F) | Significant decrease |
| Moisture removal | Aggressive | Moderate |
| Typical price | $150–$500 | $200–$600 (window/portable) |
| Power use | 300–700 watts | 500–1,500 watts |
| Best for | Cool, damp spaces | Hot, humid spaces |
| Noise level | 40–50 dB | 50–70 dB |
| Installation | Plug in and run | Window mount or portable hose |
Frequently Asked Questions
Can I use a dehumidifier instead of an air conditioner in summer?
Only if your room is not hot. A dehumidifier will not cool the air, so if the temperature is above 75 degrees, you will still feel uncomfortable. In a hot, humid climate, an air conditioner is necessary. A dehumidifier works well in cool climates where humidity is the only problem, or in basements and bathrooms that stay cool but damp.
Will an air conditioner dry out the air enough?
An air conditioner will lower humidity, but not as much as a dehumidifier. If you need humidity below 40 percent for health reasons — such as managing asthma or allergies — a dehumidifier is more effective. An air conditioner typically brings humidity down to 40 to 50 percent, which is acceptable for most homes.
Can I run both a dehumidifier and air conditioner at the same time?
Yes, and it makes sense in some situations. If a room is hot and very humid, an air conditioner cools it while a dehumidifier removes extra moisture. However, running both wastes energy if one machine can handle the job. Use both only if the air conditioner alone does not bring humidity low enough.
Why does my air conditioner make the room humid?
An air conditioner that is too small for the room, or one that cycles on and off frequently, may not run long enough to remove moisture. A unit that is the right size runs longer and removes more humidity. If your air conditioner is undersized, a dehumidifier can supplement it.
Do I need to drain a dehumidifier tank?
Most dehumidifiers have a tank that fills with water and must be emptied by hand, or you can attach a drain hose to run the water directly to a floor drain or outside. Some models have a pump that pushes water upward to a sink or window. Check the specifications before buying if you want automatic drainage.