Infographic: How Air Conditioning Works & How Much It Costs

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How does air conditioning work?

Air conditioning units come in all different shapes and sizes. You can find an air con system to cool down any property-type, from tiny flats to huge industrial spaces.

Whilst some air conditioning units may operate slightly differently, most standard units use a similar system.

The way air con works can be roughly broken down into three simple steps:

1) Warm air is drawn into the unit and cooled

The air con unit actively sucks warm air in. Inside the unit there are cold, low pressure, evaporator coils. The warm air is drawn over these coils to cool it. The cooling process happens as the refrigerant inside the coils absorbs the heat from the air and changes from a liquid to a gas.

2) Refrigerant is returned to a liquid state

For the unit to keep operating efficiently, the refrigerant needs to be returned from a gas back to a liquid form. The unit’s compressor puts the gas under high pressure, a process that creates unwanted heat. This heat is sent outside with the help of a fan. As the gas then begins to cool, it turns back into a liquid and enters the air con unit’s expansion valve where the pressure is lowered.

3) Cool air is blown out

The air con unit then blows the cooled air out into the environment using its ‘blower’. Air con units usually work on a thermostat. This means they have a thermometer sensor which will detect when the air in the room goes above a certain temperature and the unit will automatically switch on.

What Are The Four Major Components Of An Air Conditioning System?

There are several different components that make up an entire air conditioning system, but there are four that are critical that you will definitely need to have installed.

We strongly recommend that you learn about them, because a basic understanding of the component parts and how they work together can help you to get to the root of any problems you might be having with your air conditioning system.

Or it can also help you to ascertain whether the system is working as efficiently as it should be.

These 4 critical components are the evaporator, the condenser, the compressor, and the expansion valve. Let’s walk you through each one in turn.


The evaporator is one of the components found in the cold part of the air conditioning system.

Its job is  to receive liquid refrigerant, which it then turns into gas. The gas then cools and takes excess moisture from the air, in other words it dehumidifies the air. The gas also absorbs all the excess heat from the air which is then taken to the condenser.


In contrast to the evaporator, the condenser is positioned in the hot side of the air conditioning system.

The function of the condenser is to bring in the condensed refrigerant gas back outside to vent the excess heat. It will then proceed to turn the refrigerant gas back into a liquid form.


The compressor is basically a huge electric pump and is also located in the hot side of the air conditioning system.

Its job is to work along with the condenser to turn the refrigerant gas back into liquid by pressurising the refrigerant gas.

Expansion Valve

The expansion valve can be found somewhere in between the evaporator and the condenser.

It works alongside the evaporator to regulate just how much liquid refrigerant is moved there, where it then changes back into gas.

How much do air con units cost to run?

The cost of running an air conditioning unit can vary depending on several factors including:

  • The type of unit.
  • The size of the unit.
  • The size of the space it is cooling.
  • The temperature the space needs to be cooled to.
  • How often the unit is used.
  • How hard the system is required to work.

How is the cost worked out?

To work out the cost of running an air conditioning system, the unit’s British Thermal Unit (BTU) is used.

A British thermal unit is a unit of heat. It represents the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit.

For example, a unit with a BTU rating of 10,000 costs 10p per hour to run. With this information, you can work out that if a system with a BTU rating of 10,000 was left running solidly for one week, it would cost £16.80. In comparison, an air con unit with a BTU rating of 12,000 would cost £20.16 to run for one week.

Need help with installing a bespoke air con system for your commercial premises? Give our team here at Sovereign Planned Services a call on 0800 243 638 and we’ll be more than happy to assist.

Author: Gareth Whalley
Sharing my vast knowledge in the Air Conditioning and Mechanical services field especially in HVAC installation, service and maintenance across a broad range of sectors, including Healthcare, Education, Transport, Banking, Retail and Commercial developments.