7 Reasons Why Portable Air Conditioner Exhaust Hose Gets Hot

Many new owners of portable air conditioners are astounded to see the large exhaust hose because there are usually missing from product photos. In fact, manufacturers and retailers report thousands of calls asking where the exhaust goes and whether you can leave it out during installation.

As such, a hot exhaust vent causes just as much surprise. Why does the vent get hot? How hot is too hot? And what can you do if you feel that your portable air conditioner exhaust is hotter than usual? We answer these and many other portable air conditioner exhaust questions below.

The portable air conditioner exhaust vent can get hot for many reasons. However, improper venting, incorrect sizing, dirt accumulation, and an uninsulated exhaust hose are the most common reasons. Fortunately, all are issues you can fix with ease.

How Portable Air Conditioners Work

Portable air conditioners use refrigerant, typically freon, to remove heat (and moisture) from your home and dump the heat/moisture outside the house.

Refrigerant easily absorbs and releases moisture. Thus, all the portable AC has to do is draw musty indoor air into the unit and pass them around the refrigerant-filled evaporator coils.

The coils extract the heat from the musty air and also remove excess moisture from the air. Then the now-cool air returns to your home, gradually lowering your indoor temperatures.  

Then the now-warm refrigerant flows to the condenser coils, where it is compressed back into a liquid as the heat is released through a heat exchanger. The released heat is then pumped out of the air conditioner to the outdoor air.

What Does the Exhaust Do on a Portable Air Conditioner?

The exhaust vent on your portable air conditioner removes and leads the hot air from the AC outside your home.

You’re probably wondering why the central air system doesn’t have a similar exhaust system if that’s the case. The answer is that the central air system has an outdoor unit permanently stationed outside the house.

Thus, the hot air can easily move through the fins to the outdoor air. Portable air conditioner units, on the other hand, sit beside you inside the house. So, you need the means to move the warm air outside. That’s where the exhaust vent comes in handy.

Can a Portable Air Conditioner Work without an Exhaust Vent?

Yes, purpose-built ventless air conditioners work this way. They don’t use an exhaust vent. Instead, blow cool air throughout the room to make you and your guests feel cooler. 

In other words, ventless air conditioners are essentially swamp coolers, a category of dehumidifiers. They contain little ponds of water. The built-in fans blow across these ponds during operation, causing the water to evaporate into tiny moisture particles. These moisture particles interact with indoor air to cool your room.

However, it means you need to maintain the water pond. Most ventless air conditioners come with built-in reservoirs that hold between 14 and 42 pints of water.

But what about if you take off the exhaust hose in a portable air conditioner unit that typically uses one? Would it still work?

The short answer is – no. If you remove the hose, you force the air conditioner to run your room air through a cycle between cool-and-dry and hot-and-humid. This typically doesn’t cool the home much. In fact, it may leave your rooms warmer because of the heat the AC generates as it runs.

What if you switch it to “dehumidifier” mode? It wouldn’t be much better. The only difference is that the “dehumidifier” mode sends all the moisture it catches to a reservoir or sometimes drains it out of the AC via a drain hose instead of blowing it into indoor air. So, it makes the room less humid and slightly more comfortable but not cooled.

Portable Air Conditioner Exhaust Hose Gets Hot – Causes and Solutions 

So, suppose you’ve followed industry best practices and installed the exhaust pipe as required. Then, why does the pipe become too hot sometimes?

1. Improver Ventilation 

Portable air conditioners need venting. In fact, the primary purpose of the exhaust hose is to facilitate the venting of hot exhaust air out of the air conditioner and your home.

However, it’s not just about sticking the exhaust onto the portable air conditioner and hoping for the best. Instead, you must use the proper ventilation kit with the proper hose length and width.

Also, you cannot extend the hose. Altering the hose or incorrectly installing it can cause inadequate venting, overheating, and perhaps even damage to some AC parts.

Solution: Properly install the vent kit to flawlessly move heat from the air conditioner outside the house.

2. Wrong-Sized Air Conditioner 

Air conditioner sizing isn’t only critical to keeping you and your loved ones comfortable. Although that’s the main reason, the correct air conditioner size also prevents the risk of overworking the AC.

The exhaust system, for instance, can only handle a given amount of heat at a time. So subjecting it to too much heat increases the risk of overheating and melting.

Unfortunately, that’s what happens when you acquire an oversized AC, i.e., a unit too big for your home; you’re asking the exhaust hose to handle more heat than it can. So, overheating is inevitable.

Solution: The only solution here is to size your air conditioner correctly. Don’t bring home an AC that’s too big or too small for the intended application.

3. Dirty Air Conditioning Unit 

You’ve likely heard many challenges occasioned by dirt buildup inside the air conditioner. However, one of the less known consequences is exhaust pipe overheating.

Dirt buildup that impacts the free flow of air between the AC and the exhaust pipe can cause heat “stagnation” because the heat has nowhere to go. The same applies if the dirt or blockage is inside the exhaust hose. Heat stagnation can cause heat buildup, resulting in overheating.

Solution: Keep every part of the air conditioner clean at all times. And don’t forget to remove the exhaust hose and thoroughly clean it at least once every two weeks.

4. Frost Buildup 

Frost buildup isn’t an uncommon sight on air conditioners. It often occurs due to impeded airflow, causing the moisture trapped inside the air conditioner to freeze into ice.

Unfortunately, AC freezing can cause exhaust hose overheating if the ice blocks heat from leaving the air conditioner.   

Solution: The best solution is to prevent AC frosting in the first place. However, if the unit is already frozen, run the fan mode and allow it to thaw. Alternatively, call your HVAC technician.

5. The Exhaust Hose is Compromised  

There are two ways a perfectly-sized air conditioner hose can be compromised. First, the insulation may be worn or no longer present. Secondly, the hose itself could be damaged.

Both issues can cause the hose to overheat. For instance, if the hose is worn or corroded, the worn/corroded areas heat up quickly and may even melt. The same applies when the insulating material is compromised or absent.

Solution: Regular maintenance will help you keep a close eye on the condition of the exhaust hose so you can fix arising issues quickly to prevent overheating.

6. Broken Fan

Anything that impedes or compromises efficient airflow around the air conditioner and between the exhaust hose and the outdoor air can also cause the hose to overheat. For instance, a broken fan means you may experience stagnant heat within the air conditioner.

7. Low Refrigerant

Low refrigerant can also cause heat stagnation because the AC relies on efficient refrigerant circulation to move heat out of the air conditioner.

Solutions: The solutions to the various issues vary depending on the nature of each problem. The good news is that most of these issues can easily be solved through DIY, especially through regular maintenance. However, don’t hesitate to contact your HVAC contractor if you encounter tougher challenges.

Portable AC Maintenance Tips 

We’ve mentioned the importance of proper AC maintenance throughout this article. The following are some of the most maintenance tips to help you prevent or address air conditioner exhaust overheating;

  • Clean the condenser coil regularly: You need to clean the portable air conditioner coils (both evaporator coil and condenser coil) regularly to prevent frosting and poor airflow issues. Use a vacuum cleaner to blow away the dust.
  • Keep the fan blades clean: Dirty fan blades with tons of dust increase the likelihood of frost buildup. Additionally, heavy dirt buildup on the fan blades reduces the fan’s capacity to move air, resulting in poor airflow and overheating the exhaust fan.
  • Recharge the refrigerant regularly: Low refrigerant reduces heating efficiency and compromises the disposal of hot air outside the house. This can result in exhaust pipe overheating, among other consequences.
  • Replace old air conditioners: Many portable air conditioners are powerful enough to last at least 23-15 years. However, remember that the unit’s capacity to move air naturally reduces after this point. It may even struggle to compress and pup refrigerant. So, it’s best to know when to replace the unit.

Portable Air Conditioner Exhaust Hose Gets Hot FAQs

Should the Exhaust on an Air Conditioner be Hot?

Yes, the exhaust air coming out of a portable air conditioner is hot. That’s because it contains outbound heat extracted from your rooms. In fact, your AC isn’t working properly if the exhaust air isn’t hot.

How Hot is the portable air conditioner exhaust?

On average, the exhaust air leaving a portable air conditioner is 80°F to 110°F, on average. The exact value depends on many factors, including the air conditioner’s size and how hot it is out there.

Why do air conditioners vent hot air?

Portable air conditioners vent hot air because they extract heat from indoor air. They use refrigerants to remove heat from indoor air. Then the refrigerant carries this heat to the compressor, where compression action forces the heat out of the refrigerant. This heat is then dumped outside the house, resulting in cooler indoor air.

How do you insulate a portable air conditioner exhaust hose?

It’s not too difficult to insulate a portable AC’s exhaust hose if you have thermal tape. First, remove the hose from the AC, stretch it out, and wrap the thermal tape around its entire length. Then reconnect it to the portable AC. 

Can a portable AC cause fire?

Unfortunately, yes. A portable air conditioner can start a fire. However, most AC fires usually result from electric wires rather than an overheated exhaust pipe. Nevertheless, it would help if you were careful.


Unfortunately, a hot AC exhaust hose isn’t too uncommon and can cause panic among homeowners. Our advice is to stop the unit and diagnose the AC immediately if you notice overheating. If it’s not the first time, call a licensed HVAC technician. However, never run the AC without the exhaust hose.