Can a Portable AC be Used as a Dehumidifier?

Condensation on Room Window

High humidity is a problem. It makes environment uncomfortable and reduces efficiency of working. More importantly high humidity levels lead to damp and moldy environment that is bad for health. You might be wondering can you extract humidity using your air conditioner. Can you use your portable AC as a dehumidifier?

Portable ACs perform dehumidification when cooling but they are not as effective as dehumidifiers. For extracting humidity without cooling portable AC may be vented in the same room. However in partially or fully evaporative portable AC venting is required to prevent rejection of humidity in the same room. Some units have dry mode in which fan and compressor working is optimized for dehumidification.

What if your portable AC does not have a dehumidifier mode. Can it dehumidify the environment using the same principle as of air conditioning without cooling? Well, it depends on the type of unit you have.

If your model has self-evaporative technology (most of newer models) then you will have to vent it. But otherwise, you may use it as a dehumidifier, without venting or having a dehumidifier mode.

Can A Portable AC Be Used as a Dehumidifier?

During hot and humid weather in summer you may be using a portable AC for cooling your room. Besides cooling, your portable AC also performs dehumidification.

But extracting water vapors from atmosphere is a secondary function of an air conditioner. So dehumidification with your portable AC will not be as efficient as with a dedicated dehumidifier.

How Portable AC Performs Dehumidification During Cooling?

Your portable AC cools air at room temperature when it passes over its low temperature evaporator coils.

When the coils are sufficiently cool, specifically at temperature below what is called dew point, water vapors in the humid air convert to liquid state. This liquid extracted as a result of dehumidification is called condensate.

Condensate drops in the condensate pan of your portable AC. It can be removed later manually or autonomously.

Removal of humidity is partially or complete autonomous. If you have a portable AC with self-evaporative technology i.e., partially or fully evaporative portable AC then water in condensate pan is automatically removed partially or completely from condensate pan.

What happens in Dry (Dehumidification) Mode of Your Portable AC?

Some portable air conditioners are provided with ‘Dry Mode’. When you are operating your portable AC on dry mode the principle for removing humidity is exactly the same as used in cool mode.

However dry mode is more efficient. The reason is that your portable AC adjusts the fan and compressor speed to make dehumidification its priority. Fan runs at a low speed and compressors operating time is constantly adjusted according to the humidity detected by sensor. This makes dehumidification more effective and efficient.

Fan operates at a lower speed in dehumidifier mode so that evaporator coils are cold enough to extract humidity from the environment. Infact if the coil temperature is higher than a specific value the air will never reach saturation temperature and dehumidification will not occur.

The amount of humidity removed by your portable AC is depends upon the temperature below dew point (the point below which dehumidification occurs).

That is why it is highly recommended that you buy a portable AC that is accurate according to the measurement of the room (especially not larger when you need dehumidification).

What If Your Portable AC Does not have Dry Mode?

Portable air conditioners operate on vapor compression cycle. This means that despite cooling they naturally perform dehumidification. If you are running your portable AC just for dehumidification and not for cooling then this is a very inefficient way of removing humidity.

Secondly operating your portable AC this way will also cause high temperature drop in the room. The reason is obvious that your portable AC is functioning primarily for the cooling the room.

What about rainy winter days when you only need dehumidification and not cooling…

Well, there is a solution to that if you don’t have dry mode in your portable AC.

One thing that can be done is venting in the same room. This will cause the air to be cooled in your portable AC and humidity extracted from it before it is delivered in the same room. However, the cooling will be balanced by the warm air from the vent hose.

Theoretically the cooling effect will be completely balanced by the heating effect of hot air from condenser coils. However in actual the room will warm a little bit due to inefficiencies during the operation of your portable AC.

Beware to not use this strategy if you have a portable AC with self-evaporative technology like partially or fully evaporative portable AC. These units allow humidity to be rejected from the vent hose. Most self-evaporative portable ACs are partially evaporative. So most of humidity will be sprayed back into your room. This will result in net effect zero and a lot of wastage of energy.

Even if you have an AC without self-evaporative technology I would recommend that you do not use this strategy if humidity is a problem every other day. Especially if you do not want cooling with dehumidification. This is inefficient and will cause wastage of electricity.

Portable AC Vs Dehumidifier: Which Is Better?

Portable AC and dehumidifier extract humidity using the same principle i.e., cooling below dew point to condense water vapors. The working though is somewhat different.

How Dehumidifier Works Differently?

In portable AC air is cooled after passing through the evaporator coils. The heat is rejected by passing air over the condenser coils that is delivered outdoors via vent hose. Cool air is delivered indoors.

This is not the case with dehumidifiers. You do not need to vent them. Air is cooled after passing through evaporator coils. Humidity is extracted during this cooling. The cooled air is then passed through the hot coils that restore its temperature. So the dehumidification process is carried on without change in room temperature.

How Efficient is a Dehumidifier in Comparison to Portable AC?

Dedicated dehumidifier units use the same principle for removing humidity as portable AC units. Except that they do it much more efficiently, effectively and powerfully.

Dehumidifier consumes 1/10th of energy during its operation compared to a traditional air conditioner.

Moreover, the initial cost of dehumidifier is lower compared to an air conditioner.

We must compare apples with apples not oranges.

So what is the difference of performance between the dehumidification of portable AC and dedicated dehumidifier unit that have the same initial cost?

First of all, sizing of the portable air conditioner is different compared to other air conditioners. Normally air conditioners are sized for the room according to ASHRAE standards.

But due to inefficiencies in portable air conditioners, DOE uses new techniques to realize the cooling capacity. That reduced value is used to know the size of the room for which the AC will be effective.

So a portable AC may have a listed value of 14000 Btu but according to DOE standards its rating is about 7500 Btu. This means it would be able to cover a room of up to 350 square feet.

Compare that to a dehumidifier costing less than half the price of that portable AC that is able to be cover an area of 4500 square feet. This is huge amount of difference in the price and capability. In half the price area coverage increased about 13 times in dehumidifiers. But do remember cooling is considered a part of operation with dehumidification for portable AC in this comparison.

What to Choose?

Dehumidifiers are more effective and efficient in dehumidification compared to portable ACs. They have lower initial cost too. But portable ACs allow cooling and dehumidification at the same time.

So if you live in an area where it is hot and humid, portable AC is a good idea in case you don’t have a more efficient option.

But if the goal is removing humidity and temperature is not a concern, like in rainy winter days or not-so-often used place with high humidity i.e., go with a dehumidifier.