How Do Portable Air Conditioners Work? Basic Principles + Tips

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Portable air conditioners are, above all, easy to use and effective. In most aspects, the inner workings of the portable air conditioners are similar to that of a standard refrigerator.

Portable AC units are much easier to install than any other AC unit (prepared right out of the box). Obviously, they have a much greater effect on air conditioning than simple fans as well.

Two main tasks portable air conditioners are well equipped for are:

  1. Cooling down one or several rooms (primary function).
  2. Removing the humidity out of the indoor air (dehumidification is a secondary function).

We will look at how the portable air conditioners lower the room temperature and dehumidify the air. As far as dehumidification is concerned, there are major differences between the units (self-evaporation, gravity-drain, or manual removal of water).

We’ll also look at the differences in how single-hose and double-hose portable AC units operate.

On top of that, you can also check out the best and most energy-efficient portable AC units here.

Basic Cooling And Dehumidification Principle Of Every Portable Air Conditioner

Everyone will tell you that installing a portable air condition relatively easy. Unbox the unit, plugin it in, install the exhaust hose (similar to tumble dryer hose) out of the window and turn it on.

If you don’t have 15,000+ BTU portable AC unit, the standard 115/120 V power grid will more than suffice.

Nonetheless, the thermodynamic principles behind the AC units are very much the same as with all other air conditioners.

The goal is to extract the heat out of a room (or two, depending on the size) and transfer that heat outdoors. That’s why every portable conditioner has 3 key components:

  1. Refrigerant (to cool the air).
  2. Compressor (to compress the refrigerant).
  3. Fan (to move the air).

Every portable air conditioner operates based on the refrigeration cycle. Here is a quick sketch of how the refrigeration cycle looks in theory:

sketch of a refrigeration cycle on which the way portable air conditioner principles are based on

This is the most basic sense of how a portable air conditioner works:

  1. The fan sucks the hot and humid air from the indoor room inside the portable air conditioner.
  2. Inside the unit, the hot and humid air is cooled down by condensing on cold coils. This cools down the air and extracts the moisture (air moisture condenses on the coils). This is where the heat from the air is transferred to the refrigerant in the coils. That turns the refrigerant fluid into a gas; that’s why these are ‘evaporator coils’.
  3. The cool air is vented back into the room.
  4. The moisture from the air is gathered and can be vented outside or you have to manually remove the bucket.
  5. The refrigerant in gas form is compressed by the compressor on the so-called ‘condenser coils’. The heat that is released by this process is vented out of the exhaust vent installed through the window/sliding door.
  6. This cycle goes on and on.

There are two slightly different approaches when it comes to how portable AC units work. You have a single-hose and two-hose units. They are both based on the same principle, but the airflow is a bit different.

Single-Hose Portable AC Unit

Single-hose portable air conditioners are the most common ones. On average, they are also cheaper than double-hose AC units.

They have a single hose; usually installed through a window, or even through a wall. That hose only has one purpose: to serve as an exhaust vent for the hot air.

In essence, the single-hose portable air conditioner sucks in the hot room air and vents it outdoors via a single hose.

While this is the simplest way of how a portable air conditioner operates, you can obviously see that the single-hose AC unit literally sucks the air out of a room without replacing it.

The consequence of that is the lower pressure in the room. You won’t feel it in your eardrums; the fall in air pressure in not so severe.

However, the lower pressure will have to be offset in some way. In practice, the air from other rooms will be sucked in the room in which a single-hose portable air conditioner is operating.

The simple advice for a single-hose portable AC unit is to limit access to other hot air. Practically, that means you should close the door in the room where the unit is operated.

Double-Hose Portable AC Unit

Double-hose portable air conditioners are less common, more difficult to install, and more expensive. However, they can achieve higher energy-efficiency rating (EER rating) and replace indoor air with fresh outdoor air.

The way a double-hose portable air conditioner works is by using:

  1. First hose to bring the fresh air in from the outside.
  2. Second hose to vent the hot indoor air out (the single-hose portable AC units only have this one).

By having one hose to bring the air indoors, you don’t experience that lower pressure the single-hose portable AC units might cause. That means that the air is better conditioned inside the room where the double-hose unit is located.

On top of that, you get the additional benefits when operating a dual-hose portable AC unit:

  1. Higher energy efficiency. Because the unit doesn’t have to work against low pressure, the EER rating of dual-hose portable AC units can be above 10.
  2. Quicker cooling. Obviously, two hoses can condition the air much faster than a single hose.

What is surprising, however, is that you don’t see that many double-hose units. The main reason is probably that they are much more complex to make. Nonetheless, the higher EER rating makes it much more eco-friendly than the single-hose units and you can use fresh outdoor air.

For example, the Whynter ARC-14S (#3 pick) is one of the best, if not the best, dual-hose portable air conditioner.

whynter is the portable air conditioner with the highest eer rating making it the most energy efficient
Whynter ARC-14S has two vents. One to suck the air in, and the other to flush the hot air out.

With the EER rating of 11.20, it is also the most energy-efficient portable air conditioner you can find.

3 Ways Of How To Remove Moisture Portable Air Conditioners Collect

The biggest difference between how portable air conditioners work is the way of how you remove the water from the unit itself.

In fact, most of the people who are in the market for a portable air conditioner don’t exactly need a dehumidification unit. Nonetheless, all portable air conditioners are dehumidifiers. Removing moisture out of the air is the side-effect of cooling the air down.

What is more, dehumidification is something that is actually quite advantageous. Here are 3 reasons why:

  1. Summer air is humid. Too much humidity boosts mold and mildew growth.
  2. It’s easier to breathe if air is not humid.
  3. The higher the relative humidity of the air, the lower is the energy-effectiveness of portable AC units.

Portable AC units do a very good job as dehumidifiers. A single unit can remove more than 30 pints of water every day.

However, that water has to go somewhere. The key part of how portable AC units work is connected to the way they dispose of the gathered water from air moisture.

In essence, there are 3 ways:

  1. Self-evaporation (best kind). The water is evaporated and flushed out via exhaust vent with the hot air. Most modern portable air conditioners use this system.
  2. Gravity-drain with optional built-in pump (still good). The collected water is pumped out via a hose.
  3. ‘The bucket’ (not recommended). Some old-school portable AC units have a bucket. There the water is collected and you have to manually empty the bucket when it’s full. Buying such a portable AC is, for lack of a better word, a bad idea.

Summary: Portable AC Unit Inner Workings Are Complex But Handling Is Easy

Portable AC units are quite similar to refrigerators. They have a refrigerant, compressor and the inner workings of expanding gas and compressing it again and again.

Nonetheless, the same level of technical expertise is needed for operating a portable air conditioner as is for the fridge.

Once you plug it in, it’s extremely easy to operate and keeps your home cool.

10 thoughts on “How Do Portable Air Conditioners Work? Basic Principles + Tips”

    • Hello Sue, a single-hose air conditioner sucks the warm indoor air and transfers that heat outsize via the exhaust vent. The text there is not as exact as it should be, we’ll have it corrected, thank you for pointing it out.

  1. What does the fan mode do on a single-hose A/C. I can hear the compressor kick on and off in that mode. Is it drawing in fresh outside air, recirculating the inside air or could it still operating as a cooling system?

    • Hello Betsy, the function of the fan is to move the air around. Specifically, it draws the hot indoor air into the single-hose AC. The air is cooled down and returned into the room, while the hot air (the consequence of cooling air) is expelled outdoor via the exhaust went.

    • Hello Erik, pointing it toward you will give an impression of the room being cooler than it actually is. Generally, the hot air is lighter than cold air; hence it is located more towards the ceiling. Having vents pointed upwards might, in theory, push that hotter air down. However, this should not have any significant effect on the overall average room temperature.

    • Hello Kathryn, you basically can’t use a portable air conditioner without a window. Every air conditioner needs to have thermal interaction between indoors and outdoors; in the case of portable AC units, that’s a window or a sliding door.


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