Three-in-one portable air conditioner units are quite the all-in-one solution: they provide cooling, a fan, and a dehumidifier in a single appliance. For those of us in humid climates without central air (or with an upstairs that never seems to cool down), buying one of these really seems like a no-brainer on the surface. You get both an air conditioner and a dedicated dehumidifier in one, plus a fan to top it all off. But is it really as good as it seems? To know for sure, let’s look at what both a three-in-one AC unit and a dehumidifier are supposed to do on their own.

Air conditioners are obviously intended to lower your indoor temps. But what you might not know is that, as part of that cooling process, some of the warm, humid air in the room passing over the refrigerant-filled evaporator coils will condense into water. It’s removing some, but not all, of the moisture in the air. It’s really just a secondary benefit to the cooling. That’s what’s interesting about these three-in-one models: In addition to cooling, they also have a drying mode that prioritizes dehumidification over cooling. Still, that dry mode is not the same as a dedicated dehumidifier that can maintain a set humidity level or tackle major moisture problems.

If the room feels a little balmy from time to time, a three-in-one AC unit can do a perfectly fine job of getting the place feeling comfortable again. But if you’re living in a super humid environment or trying to get a serious moisture problem under control, a standalone dehumidifier really can’t be beat. Rather than focusing on temperature, it has a sole purpose: to remove excess moisture from the air. Because the entire appliance is built around humidity control, it can remove substantially more moisture than a three-in-one AC that simply gives you a drying feature.

Let’s talk about numbers: High-quality dehumidifiers can remove up to 70 pints of water a day. Meanwhile, 3-in-1s might only take out 40 pints or less. The tradeoff, of course, is that standalone dehumidifiers can run hot. While that extra warmth won’t raise the temp much, it can still make a room feel slightly warmer. During the summer months especially, that might be a problem for you.

Choosing one over the other will ultimately come down to your goals. If you deal with both heat and humidity, the three-in-one air conditioner can do both well. But if the humidity in your house remains a problem, you may need a dehumidifier as well as a standalone AC. That way, you can get both dedicated cooling and dedicated dehumidification at once. Just be careful when running both, as this could be a fire risk.