How does air conditioning work? Understanding the basics
Air conditioning is becoming more common in UK homes, especially as summers get even warmer. But how does it actually work?
In this guide, we’ll break down how that happens, what different systems do, and how to get the best from them.
Published on 22nd May 2026 by:
Edward Weatherall, Commercial Delivery Manager, Installs
What does air conditioning do?
Air conditioning does more than just lower the temperature. As it runs, it also helps reduce humidity, filters out dust and particles in the air, and keeps air circulating so rooms feel fresher and less stagnant. That combination is what makes a room feel noticeably more comfortable, especially in warmer weather or stuffy spaces. Our systems also provide efficient heating when temperatures drop in the Winter.
How does AC work?
In cooling mode, your air conditioning takes heat out of your home and moves it outdoors. This involves:
- Warm air from your room is drawn into the indoor unit (the evaporator). As it passes over cold coils filled with refrigerant, the heat from the air is absorbed.
- As the refrigerant absorbs heat, it changes from a liquid into a gas. That gas is then pushed through the system by a compressor.
- The refrigerant gas travels to the outdoor unit (the condenser), where the heat is released into the outside air.
- As the heat is released, the refrigerant cools back into a liquid so it can be used again.
- At the same time, the indoor unit keeps drawing in more warm air and sending cooled air back into the room.
This runs continuously in the background, quietly maintaining the temperature you’ve set it at.
How does air conditioning work in a house?
In most homes, air conditioning systems are typically split between an indoor and an outdoor unit working together. The indoor unit takes warm air from the room, removes the heat, and sends cooled air back inside. The outdoor unit then handles the heat that’s been extracted and releases it outside the home.
These two units are connected by small pipes that carry refrigerant between them. A thermostat or remote control manages the system, switching it on and off as needed to maintain a steady temperature without you needing to adjust it constantly.
How do different types of air conditioning work?
There isn’t a one-size-fits-all approach to air conditioning, so it’s important to choose a system that suits your home or workplace.
Ductless air conditioning (split systems)
Ductless systems are one of the most common options in UK homes. They use a wall-mounted indoor unit connected to an outdoor unit, cooling a specific room or zone.
Because there’s no ductwork involved, installation is relatively straightforward. They’re also much more flexible. In fact, you can control individual rooms separately, which helps you cool only the spaces you’re using.
Ducted air conditioning
Ducted systems take a more whole-home approach. A central unit pushes cooled air through a network of hidden ducts, with vents in different rooms.
This setup is often used in larger homes where a consistent temperature throughout the property is preferred. The system itself is out of sight, but installation is more involved and usually planned during renovation or construction. British Gas doesn’t offer this type of air conditioning.
Portable and window air conditioners
These are standalone units designed for single rooms. They work by drawing in warm air, cooling it, and venting heat outside through a window or hose.
They’re useful for short-term or occasional use, but they’re generally less efficient and can be noisier than fixed systems.
Are there other benefits to installing air con?
Air conditioning does more than just cool your home — it can improve comfort, air quality and even wellbeing in everyday life:
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Purification: Advanced filtration systems used with modern air conditioning can help purify indoor air - capturing a high proportion of airborne particles and reducing dust, smoke and pollen by up to 95%.1
Reduces humidity indoors: Air conditioning can remove excess moisture from the air, helping to create a drier, more comfortable environment, especially useful in rooms that feel stuffy or damp.
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Helps reduce the risk of overheating: By keeping indoor temperatures more stable, it’s easier to avoid excessive heat, which can contribute to dehydration, heat exhaustion and other heat-related issues.
Supports better sleep: A cooler bedroom can make it easier to fall asleep and stay asleep, helping you feel more rested and comfortable through the night.
Does air con just cool a room?
In fact, many modern air conditioning systems can also heat your home. They work by reversing the cooling process, drawing heat from the air outside and bringing it indoors. Because they move heat rather than generate it, they can be a highly efficient way to warm your space.
With British Gas, our air conditioning units offer rapid, on-demand heating and cooling.
How to use an air conditioner effectively
Setting your temperature somewhere around 18-21°C2 is usually enough to balance comfort with savings without overworking the system. You should also make sure you keep doors and windows closed whilst running your air con as it helped cool air stay where it’s needed.
If you don’t need to cool the whole home as well, focusing on the rooms you’re actually using can make a noticeable difference in energy use.
Does air conditioning use a lot of electricity?
Running costs depend on your system type, how often you use it, and the size of your home.
Modern air conditioning systems are designed to be up to A++ efficient, particularly when cooling individual rooms rather than an entire property all at once. Features like timers and smart controls can also help you manage usage more effectively.
Thinking about air conditioning for your home?
A well-chosen air conditioning system can make a real difference during warmer months, especially if your home tends to hold heat or feels stuffy in summer.
With British Gas, you can get expert advice on the right system for your home, along with professional installation and ongoing support to keep everything running smoothly. Get a quote today to see your options.