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Comment by hachari | Hacker News Reader

A dehumidifier is essentially an air conditioner that dumps heat back into your living space.

What you are doing sounds inefficient.

The dehumidifier does use power and produce heat which must be removed from my apartment by the air conditioner.

Because it's less humid, I can maintain a higher indoor temperature and still be comfortable, meaning the air conditioner needs to run less.

Do I use net less energy? In my case, yes, but your mileage may vary depending on your equipment, insulation, etc.

He's saying that you have two air conditioners: one that vents heat inside your house and one that vents heat outside your house.

Your dehumidifier and your air conditioner are mechanically identical. The only difference between the two is where the waste heat goes. The exact same device is called a 'dehumidifier' if the waste heat is vented indoors and an 'air conditioner' if the waste heat is vented outside.

There's not really any efficiency gains from running a dehumidifier to reduce air conditioner use. They both use the same power and have the same effect on the absolute humidity, so you might as well just run the air conditioner (unless you want it to be warmer).

There's also dessicant dehumidifiers that don't use a refrigeration cycle. They do also warm the air a bit but may be more efficient per mass of water removed from the air, depending on the temperature and humidity range.

I ended up buying a dehumidifier to complement my AC, which is ancient and can't seem to keep up with the humidity in the summer.

Before the dehumidifier I could get the room cool, but it still felt sticky. With both I'm able to keep the humidity at bay and cool the room as well.

Yep. They're adding heat to the inside of their home. They need to use an AC unit to remove the moisture and pump the heat outside.

I do have an air conditioner (well, an air-source heat pump), but it doesn't adequately remove enough moisture before the indoors gets too cold. It's possible this is not properly sized, but I cannot change it because I rent.

In my case I did some tests, and the additional power usage of the dehumidifier is way more than offset by the power savings I realize by running the air conditioner less frequently. This only works because the dehumidifier enables me to be comfortable at a higher indoor temperature.

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