Why Is My Portable Air Conditioner Not Cooling?

Portable ACs are a great way of cooling rooms of houses of a smaller size for which you do not want to spend extra bucks on installing a central air conditioning or HVAC system. They are energy efficient and can provide excellent cooling for small-sized rooms. But sometimes a portable AC is not working properly, and you may wonder: why is my portable air conditioner not cooling?

There could be several reasons why your portable AC is not cooling your room sufficiently. One of the simplest reasons could be that it is not powerful enough for the space where you would like it to cool!

You should check out whether the unit’s cooling capacity is powerful enough to cool a room of your size and in your climatic conditions before buying.

Other reasons could be that the air filter is dirty or the refrigerant is too low. In this article, we will discuss why your portable AC might not be doing its job efficiently and what you can do about it.

How Does My Portable Air Conditioner Work?

Before we dive into the reasons why your portable AC might not be cooling, it is first important to understand how it cools the room. This is a bit different than normal ACs because all units of a portable AC are inside the room itself.

Portable air conditioners are of two types: single hose and double hose. While the single hose AC uses the hot air inside the room for cooling, dual-hose ACs use outside air. The cooling mechanism in both remains the same.

Inside the AC, there is a refrigerant passing through the evaporator coils. It absorbs the heat of the air (indoor air or outdoor air, depending on the number of hoses) and converts it from liquid to vapor. 

The low-pressure and temperature vapor refrigerant enters the compressor and is compressed into high-pressure and temperature vapor refrigerant. 

This vapor refrigerant enters the condenser tubes, where water vapor is condensed by throwing the heat into the outside environment. The vapor refrigerant changes back into liquid refrigerant at the same temperature and pressure. 

The liquid refrigerant moves to the expansion valve, where its temperature and pressure are drastically reduced. The low temperature and pressure liquid refrigerant again moves to the evaporator coils. 

The cycle continues again and again to provide a cooling effect. The water vapor that condenses during the process is expelled either through self-evaporation or a moisture bucket that you need to manually drain out periodically.

Related article: What Are The Types Of Air Conditioners

Why Is My Portable AC Not Cooling My Room?

1. Choked Air Filter

The air filter in your portable air conditioner helps trap the dust and dirt particles so that you can breathe clean and pure air. 

If you don’t clean this air filter regularly, it will become choked with dust and dirt. Consequently, your portable air conditioner will not function properly. The fan may run once you turn on the portable air conditioner, but it cannot blow cool air into your room.


Remove the air filter from your air conditioner and clean it every month. If the air filter is washable, you can wash it with mild detergent and water. 

After washing, allow it to dry completely, and then reinstall the air filter into the portable air conditioner.

2. Low Refrigerant

Refrigerant is the fluid used in your portable air conditioner that absorbs the heat from your room and provides cool air. If the refrigerant starts leaking from your portable air conditioner, it cannot effectively cool your room. 


Call an HVAC technician to re-fill the right amount of refrigerant in the air conditioner.

3. Your Thermostat Is Faulty

The thermostat in the air conditioner helps sense the temperature of your room and sends the information to the air conditioner. For instance, if you set the temperature to 68℉, then the thermostat will work to maintain this temperature by controlling the flow of electricity to the compressor of your portable air conditioner. 

The thermostat allows the electricity to flow to the compressor when it senses the temperature exceeds 59℉. It stops the electricity flow to the compressor when it senses the temperature in your room reaches 59℉.

So, the thermostat plays a vital role in maintaining the desired temperature. If it becomes faulty, your portable air conditioner cannot maintain the desired room temperature.

Also read: Air Conditioner Blows Too Cold


Sometimes the battery becomes low, which prevents the thermostat from functioning and detecting the temperature correctly. In this case, we suggest replacing the batteries of the thermostat.

Dust and dirt may accumulate on the thermostat, which may also cause it to not detect the temperature correctly. You can clean your thermostat and check whether you have resolved the issue once again. 

If the problem persists, then call your local AC repair company. If the thermostat is broken, the HVAC professional may ask you to replace the thermostat with a new one.

4. Your Portable AC Is Not Powerful Enough

You should check the specifications and mainly the cooling capacity when shopping for a portable air conditioner. An incorrect size portable air conditioner will not cool your room effectively.

The cooling capacity is the amount of heat removed by your portable air conditioner in one hour and is measured in British Thermal Units (BTU). One BTU is the amount of energy required to increase or decrease the temperature of a pound of water by 1°F.

If you use a portable AC with a lower cooling capacity than required, it will be unable to effectively cool a room. On average, 12,000 BTUs are enough to cool a 400 to 500-square-foot room.

Similarly, having a large cooling capacity portable air conditioner in a small room will cool the room quickly, but this may be energy inefficient.


Remember, selecting an adequate portable air conditioner depends on many factors like the size of your room, climatic conditions, and the number of people expected to stay in the room regularly.

Below you will find a chart with the approximate BTU required based on the square feet of your room.


5. The Evaporator Coils Are Dirty

The evaporator coils in the portable air conditioner is a heat exchanger. It absorbs the heat of your room and changes it into vapor, allowing your room to cool. The refrigerant flowing in the evaporator is at low pressure and low temperature. 

But when the evaporator’s coils get dirty, there cannot be effective heat transfer between the room air and refrigerant, which decreases the efficiency of the portable air conditioner. Your room will not get cool properly with a dirty evaporator coil.


Try to clean the evaporator coils from time to time so that they do not impede your air conditioner’s cooling functionality.

6. Close Your Doors and Windows

If there is a gap in your door or windows, a portable air conditioner will not cool the room effectively. The inflated air will decrease the efficiency of your air conditioner.


Try to close all the doors and windows and then switch on your AC.

7. Exhaust Hose of Your AC Is Leaking

Your portable air conditioner will not cool effectively if the exhaust hose leaks. The exhaust hose removes hot air from your room. But if it is leaking hot air into your room, your room will not get cooled effectively.

If your room has an exterior window, you can purchase a window venting kit to prevent your portable AC from leaking hot air back into your room. A window venting kit has all the necessary components and parts and will make the installation process more straightforward.

This window venting kit is designed to work on both up-down opening windows and side-to-side opening windows.


Obstructions like leaves or debris can block the airflow. So you should check the exhaust hose from time to time to ensure that it is unblocked.

Related article: Air Conditioners Buyer Guide

Final Thoughts

If you have a portable air conditioner and it is not cooling your room in the hot summer months, you may become worried and frustrated. In this article, we have listed a few possible reasons why your portable air conditioner does not cool your room, along with solutions.

We hope this article can guide you in fixing your portable air conditioner so that you can continue to cool your home in the warmer months!

Related article:

HVAC Maintenance Tips – Everything You Need To Know

Can We Use AC When Water Is Leaking?

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