Air Conditioner Dry Mode VS Dehumidifier Explain: Same?

“AC on dry mode is the same as a dehumidifier. Right?”

Well, yes and no. We got a few of these air conditioner dry mode vs. dehumidifier questions by now. It seems like a good idea to adequately explain the difference between a dehumidifier and an aircon dry mode.

That word – ‘adequately’ – is important here. That’s because pretty much any article on the internet tells you that “AC dry mode is the same as a dehumidifier”. This applies to all AC dry modes – from mini split dry mode, portable AC dry mode, and even heat pump dry mode.

That is not entirely wrong, of course. Both AC and a dehumidifier lower indoor relative humidity levels. They even use the same process of condensation to achieve this. But there is a key difference between an AC dry mode and a dehumidifier. Namely, everybody explains that both of these appliances do the following 2 things:

  1. Reduce humidity levels. Something like a reduction from 70% relative humidity to 30-50% relative humidity.
  2. Do not change the indoor temperature. If you start running AC dry mode or a dehumidifier at 72°F, the indoor temperature will remain constant at 72°F.

The 1st statement is true: That would mean that the AC dry mode and a dehumidifier are the same. The 2nd statement, however, is false.

Here is what happens with the temperature:

  1. Dehumidifier doesn’t decrease or increase the temperature; it stays constant.
  2. Air conditioner dry mode does decrease the temperature.

To explain why this happens and that AC dry mode and dehumidifier are functionally not the same thing, let’s compare how air conditioner dry mode works vs how a dehumidifier works:

How AC Dry Mode Works (Compared To Dehumidifier)?

Now, as we have written in this post about dry mode in air conditioners, every AC unit has several modes, including a dry mode. Let’s first look at how dry mode works and then compare it with how a dehumidifier works (more on the inner workings of dehumidifiers here):

  1. The fan creates an airflow over indoor evaporator coils.
  2. Refrigerant decreases the temperature of the evaporator coils; we get the cold coils.
  3. When the moist air comes into touch with the cold coils, the air moisture condenses on these coils (much the same way as you can see droplets on a beer glass). This condensed water drips to the drip fan outdoors via the condensate hose.
  4. The resulting air that is being returned into the room is drier but also colder (no heating included; this will become relevant later on).
mini split dry mode vs dehumidifier
Mini split air conditioner: You can only see the cold evaporator coil in the indoor unit.

Here is how the dehumidifier reduces moisture (you will see that you have 1 additional, but very important step):

  1. The fan creates an airflow over indoor evaporator coils.
  2. Refrigerant decreases the temperature of the evaporator coils; we get the cold coils.
  3. When the moist air comes into touch with the cold coils, the air moisture condenses on these coils.
  4. This dry and cooler air now passes over hot coils. These bring the air temperature back to room temperature (that’s why a dehumidifier doesn’t change the indoor temperature).
  5. The resulting air being returned into the room is drier and has the same temperature as the input air.
dehumidifier is not the same as air conditioner on dry mode
Dehumidifier: You can see that it has both the cold coil (evaporator) as well as hot coil (condenser). This hot condenser is the key difference between an AC dry setting and a dehumidifier.

As you can clearly see, the dehumidifier has additional hot coils that warm up the cooled air. Air conditioners don’t have that.

There are two key results:

  1. A dehumidifier will not decrease the temperature. The air conditioner running on dry mode will decrease the temperature.
  2. It is more energy efficient to run an air conditioner on dry mode than to run a dehumidifier. That’s simply because the dehumidifier has to work a bit harder to heat those hot coils as well.

All in all, yes, the dehumidifier and AC dry mode have the same purpose: to decrease indoor relative humidity levels. However, the dehumidifier includes additional heating coils to bring the temperature of output air in line with room temperature, while the AC unit on dry mode outputs cooler air (thereby cooling your home a bit as well).

Leave a comment