AC Compressor vs Condenser: The Differences

All air conditioners (central and ductless/mini-splits) have an indoor unit and an outside unit. The inside unit is basically the evaporator coil while the outside unit comprises both the compressor and condenser coil.

Most folks also refer to the outside unit as the condenser unit. It is there not surprising that there are many homeowners who can’t tell the difference between the condenser and the compressor especially in terms of their functions.


So, what is the difference between an AC’s compressor and condenser? And how do these 2 components function?

The compressor compresses the refrigerant gas thereby increasing its temperature, relative to that of the surrounding air. On the other hand, a condenser coil is a heat exchanger where the refrigerant gas loses heat to the surrounding air and in the process turn from gas to liquid.

In other words, when the refrigerant absorbs heat from the indoor air (inside the evaporator coil). It releases the heat to the outside air inside the condenser coil. That’s made possible by the compressor which increases the refrigerants temperature thereby making heat transfer possible.

A condenser is a heat exchanger while a compressor is not. Inside the condenser coil, the refrigerant releases heat to the surrounding air. Also, the refrigerant goes through a phase change (gas to liquid) inside the condenser while there is no change in phase inside the compressor.

Both condenser and evaporator coils are heat exchangers. Inside the evaporator coil, the refrigerant absorbs heat from indoor air (cools it) and changes from liquid to gas. Inside the condenser coil, the refrigerant releases the heat to the surrounding air and turns from gas to liquid.

Because of wear and tear during its work, a compressor is more likely to fail than the condenser coil. When that happens, most homeowners are often confused on whether to replace just the compressor or the entire outside unit.

But what should you do? What about when the condenser fails but the compressor is still good. What should you do?

If the compressor fails, you can replace only the compressor and leave all the other parts intact. However, if the condenser fails, the best option would be to replace the entire outside unit (both condenser and compressor).

AC Compressor vs Condenser vs Evaporator

To understand the differences between an air conditioner’s compressor and condenser, you must first understand how the entire air conditioning system works.

As I have mentioned above, an air conditioner has 3 main components:

  • Evaporator
  • Compressor
  • Condenser

A refrigerant is cycled between this 3 components to cool or even heat the house. The refrigerant changes state from gas to liquid and back to gas easily thanks to its very low boiling point.

By changing from liquid to gas (evaporation) the refrigerants takes away heat from inside the house and a lot of heat for that matter due to its high latent heat of vaporization.

Inside the house, the refrigerant enters the evaporator coil as a very cold liquid.  The evaporator fan pulls warm air from the house and forces it through the evaporator coil.

Because of the difference in temperature, the refrigerant absorbs heat from the indoor air and cools in in the process. Cooled air is circulated back to the house.

After absorbing enough heat from the air, the refrigerant vaporizes and is ejected out of the evaporator towards the compressor.

Let us now see how both the compressor and condenser coil work hand in hand in helping the refrigerant release the heat it absorbed indoors to the surrounding air.

AC Compressor


To start with, a compressor is very small relative to the size of the condenser. A condenser is a big metallic box with copper tubes coiled back and forth to form a shell and a compressor is located at the very bottom.

The compressor receives the refrigerant from the evaporator coil in gas form. It is important that all the refrigerant is vaporized before entering the compressor. That is made possible by a device known as an expansion valve.

Compressors can only compress gas. Trying to compress liquids will definitely damage the compressor.

A compressor basically works like a pump or a human heart. It gives the refrigerant the force it needs to move through the condenser coil.

Apart from that, the compressor has another vital function. You see, after absorbing heat from the indoor air, the next step is to remove the heat from the refrigerant so that it can go back inside the house for more cooling.

That is precisely the reason why both compressor and condenser are located outside the house. The problem though is that since that would be during summer, the outside air is just as hot as the refrigerant gas.

As you already know, for heat transfer to take place, there must be a difference in temperature between the 2 mediums. And that is where a compressor plays its role.

By compressing the refrigerant gas, it is not just the pressure of the refrigerant that increases. Its temperature increases as well. The more you compress a gas the more its temperature increases.

In a nutshell, we can say that the function of a compressor in an air conditioning system is to increase the pressure and therefore the temperature of the refrigerant so that it (the refrigerant) can release heat to the surrounding air.

AC Condenser

As I said and as you already know, the condenser coil is a huge thing. Size in a condenser coil is very important. It increases the surface area for heat exchange.

When there is a lot of the external air in contact with the hot refrigerant, the rate of heat exchange between the 2 mediums will be even higher. This also explains why the condenser (and also the evaporator) are made up of rubes looped round a frame.

The refrigerant gas enters the condenser coil as a high-pressure superheated gas. Due to the difference in temperature between it and the surrounding air, heat will be transferred from the refrigerant to the outside air.

To accelerate this process is a condenser fan installed at the top of the unit. The fan blows cooler air at a very fast speed. The cooler air quickly absorbs heat from the refrigerant and dissipates it to the surrounding.

By the time the refrigerant is exiting the condenser coil, it will have lost so much heat that it will have changed from gas to liquid.

To lower its temperature even further the refrigerant goes through a throttling device known as an expansion valve where it emerges as a very cold liquid.

The cold refrigerant liquid then enters the evaporator coil and the process is repeated over and over again until the house is sufficiently cooled.

How Do I Know If My AC Compressor or Condenser is Bad?

It is not easy to tell if you are dealing with a bad compressor or condenser. The signs for both are almost the same, the main one being no or ineffective cooling.

The best thing to do in such a scenario would be to have an HVAC technician come over and have a look. Actually, there are very few AC problems that can be DIYed by the average homeowner.

Nonetheless, the following are the signs that you are dealing with a bad compressor or condenser:

  • Ineffective cooling. The cooling capability of the AC will be greatly affected if either the condenser or compressor is bad/
  • Unusual rattling, growling or screeching noises from the unit.
  • When you are having a hard time trying to start the air conditioner.
  • AC circuit breaker keeps tripping.
  • Noticeable leaks from the unit. Way higher than the usual condensation amount.

Wrap Up

And basically those are the differences between an AC compressor and condenser. You know also know how an evaporator works in the cooling cycle. I hope that this guide was helpful and that it is exactly what you were looking for.