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Can You Use an Air Conditioner Sideways?

Air conditioners come in different sizes; some are big enough to cool buildings; others are small units for individual rooms. Still, even smaller air conditioners are frequently wider than some windows. A simple solution will be to turn the AC on its side, right? Not so!

You can’t use an air conditioner sideways, as it’s not designed to function that way. Elements like condensate drains will malfunction if turned sideways. More crucial is the compressor, which will quickly fail, and may cause a fire if it explodes from inadequate or improper lubrication.

This article explains in great detail how an air conditioner works and why using one sideways will not work, but instead cause damages. It also discusses ways to use an air conditioner without resorting to turning it sideways.

Can You Use an Air Conditioner Sideways

How does an air conditioner work?

Unlike what most people think, air conditioners do not cool the air. The work of an air conditioner is to remove heat from a room. Air conditioners use two sets of connected coils with a refrigerant fluid constantly flowing inside them to extract heat. 

The two coils are located at both ends of the air conditioner; one coil sits in the part of the air conditioner inside the house, the other coil stays outside. The coil in the room is colder than the room temperature, while the coil outside is hotter than the surrounding air. 

The second law of thermodynamics explains that heat moves from a hot area to a cold area. As such, warm air in the room will lose its warmth as it blows over the cold coil. This cooled air is then returned to the room, and the cycle continues until the room is sufficiently cooled.

Can You Use an Air Conditioner Sideways

Now, you may wonder how the coil manages to remain cold if warm air is continuously blowing over it. The answer is the refrigerant in the coils. The refrigerant is a fluid with a low boiling point, so low that as warm air flows over the coils, the refrigerant heats up, turns to gas, and flows to the other coil outside.

Again by heat transfer, the hot gas loses the heat and turns back to liquid as a fan blows cool air over it. The liquid returns to the coil in the room, ready to be turned into a gas as air warm air blows over it.

To continuously move the refrigerant around the system, the air conditioner uses an evaporator, a compressor, a condenser, and an expansion valve. These four are the major elements in any air conditioner. 


The evaporator is the cold coil in the room, where the refrigerant turns to vapor. 


Vapor from the evaporator enters the compressor. The compressor’s job is to compress the vapor, make it smaller and compact. As a result of the compression, the vapor leaves the compressor at a much higher pressure and temperature than when it left the evaporator.


When the refrigerant reaches the condenser, its pressure and temperature are higher that of the air outside, and so using as a fan blows over it, it loses heat to the atmosphere and condenses into a liquid.

Expansion Valve

The expansion valve is right before the evaporator. Its job is to reduce the pressure of the condensed refrigerant so that as it enters the evaporator, the boiling point is low enough that it will boil as it absorbs heat from the air, turning into vapor and beginning the cycle again.


What happens when you use an air conditioner sideways?

Having seen how an air conditioner works, this is what will happen if you use an air conditioner on its side.

Compressor Burnout and Possible Fire 

The compressor uses gears and other moving parts to compress the gaseous refrigerant. These parts of the compressor need to be continuously lubricated if they are to function correctly. As such, compressors get equipped with lubricating oils. The lubricant is specially formulated to deal with the high pressures and temperatures that a compressor handles and is located at the bottom of the compressor. 

The compressor oil does more than lubricate; it also absorbs heat from the compressor, and depending on the type of compressor, it may also serve as a seal, similar to a gasket. While the parts of the compressor are fixed, gravity is what keeps the oil in the bottom of the compressor. 


As such, if you turn an air conditioner sideways, the compressor and the lubricant turn as well and will flow out. 

Thus parts of the compressor will be forced to work without lubrication, thereby causing the compressor to overheat as there is not enough oil to absorb the thermal energy. In addition to the heat buildup in the compressor, more heat is generated by friction from the unlubricated and continuously rotating parts of the compressor mechanism. 

Eventually, the compressor will get damaged from overheating, and In extreme cases, overheated compressors can explode and catch fire

Rainwater Will Get Into the AC

Air conditioners have vents on the sides and bottom for ventilation and to expel the heat extracted from the condenser. By turning the air conditioner on its side, these vents face upward and will allow damage-causing rainwater into the air conditioner.

Even if you could prevent water from entering by covering the vents, it prevents hot air from leaving. As such, you end up again with a heat problem.  

Condensation Will Drain Incorrectly

Condensation is the process where moisture in the air turns from gas to liquid as it cools. Warm air from the room cools down as it blows over the evaporator, this causes the water vapor in the air to condensate as droplets on the coils of the evaporator. The droplets fall by gravity and are collected by the condensation pan and transported out of the air conditioner by the condensate drain line.

Can You Use an Air Conditioner Sideways

If you turn an air conditioner on its side, the condensation will drip into the air conditioner, causing damage to the unit and possibly leak into the walls and floor of your home.

All of the reasons listed above, but especially compressor damage and explosion is why manufacturers recommend that you position the air conditioner correctly before use.

What other options, if not sideways?

You should not use an air conditioner sideways; you also should not suffer sweltering heat or sleep in a pool of your sweat. Here is a list of alternative ways you can air-condition a room. 

Expand the Window

If the house is a wooden framed one, you can expand the window by cutting either or both sides of it to accommodate the air conditioner. However, this solution is not advised for brick buildings and rentals.

Make an Opening in a Wall for the Air Conditioner

Again this option is only viable for a wooden and non-rental house. Although some landlords may not object to the modification, seeing as it increases the value of their property.

Consider Casement Air Conditioners

Casement air conditioners are designed to be slimmer but taller to fit into a casement or sliding window. You can take advantage of this type of air conditioner for a narrow window. Cover what space remains between the top of the air conditioner and the top of the window with plywood, or plexiglass which will allow some light into the room. Casement windows are typically less energy-efficient and more expensive than a window air conditioner.

Portable Air Conditioners

A portable air conditioner is perhaps the simplest solution to a narrow window as it requires the least amount of modification. Most units come with an easy to install window kit. 

Portable aircon

A significant drawback of portable air conditioners is that they can be noisy, as all the parts of the machine sit in your room, unlike a window air conditioner where the compressor and condenser are outside. Still, newer models incorporate noise reduction technology so that you can sleep better at night. 


The design of an air conditioner relies much on gravity. If used sideways, one or all of the following may happen:

  • Compressor damage and possible fire
  • Rainwater will get inside the air conditioner
  • Condensation will drain incorrectly

Significantly smaller windows present a unique challenge to air conditioner cooling, often being too wide to fit in windows. You can modify the window, get a casement air conditioner, or a portable one, but never use an air conditioner sideways as doing so will damage the unit and possibly your home.


  • Jake Alexander

    Jake is a freelance writer from Pennsylvania who enjoys writing about science and sports. When he's not writing for Temperature Master, he can be found watching the NFL or playing basketball with his friends.

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