A split system air conditioner is an air con unit made up of two separate parts, an indoor unit mounted on a wall or ceiling and an outdoor condenser sat outside the property, connected by refrigerant pipework and electrical cabling.
It’s the most common type of air conditioning fitted in UK homes today, largely because it’s more efficient and considerably quieter than older window mounted or portable units that house everything in a single box.
This guide explains exactly how a split system air conditioner works and why it’s become the standard choice for homeowners across the North West, Yorkshire and the Midlands.
What Is A Split System Air Conditioner?
A split system air conditioner is an air conditioning unit that separates the noisy, heat generating components from the quiet, air cooling components, housing them in two physically distinct units rather than one combined box.
The indoor unit contains the evaporator coil, blower fan and air filter, while the outdoor unit houses the compressor, condenser coil and expansion valve, with copper refrigerant lines running between the two through a small hole in an external wall.
This separation is exactly where the “split” in split system air conditioner comes from, and it’s the fundamental design used across virtually every wall mounted, multi split and ducted air con system sold in the UK today.
How Does A Split System Air Conditioner Actually Work?
A split system air conditioner works by continuously cycling refrigerant between the indoor and outdoor units to absorb heat from inside your home and release it outside. Warm room air is drawn across the indoor unit’s cold evaporator coil, where the refrigerant inside absorbs that heat and cools the air before a blower fan pushes it back into the room.
The now warmer refrigerant then travels through copper pipework to the outdoor unit, where the compressor pressurises it and the condenser coil releases the absorbed heat into the outside air, with a fan helping to dissipate that heat before the cooled refrigerant heads back indoors to repeat the cycle.
Most modern split systems also run in reverse for heating, absorbing heat from the outside air, even on cold days, and releasing it indoors, functioning as an efficient heat pump alongside standard cooling.
What Are The Main Components Of A Split System Air Conditioner?
The main components of a split system air conditioner are split between the indoor and outdoor units, each playing a distinct role in the overall cooling and heating cycle.
| Location | Component | Function |
| Indoor unit | Evaporator coil | Absorbs heat from indoor air using cold refrigerant |
| Indoor unit | Blower fan | Circulates cooled air back into the room |
| Indoor unit | Air filter | Removes dust and particles before air passes over the coil |
| Outdoor unit | Compressor | Pressurises refrigerant, raising its temperature |
| Outdoor unit | Condenser coil | Releases absorbed heat into the outside air |
| Outdoor unit | Expansion valve | Reduces refrigerant pressure before it returns indoors |
| Both units | Refrigerant lines | Copper pipes carrying refrigerant between indoor and outdoor units |
What Types Of Split System Air Conditioners Are Available?
The types of split system air conditioners available range from single split units covering one room through to multi split systems capable of cooling several rooms from a single outdoor condenser.
- A single split system connects one indoor unit to one outdoor unit and remains the most common setup for bedrooms, home offices and living rooms across UK homes.
- A multi split system connects two to five indoor units to one shared outdoor condenser, which is a popular choice for family homes across the Midlands wanting several rooms cooled without cluttering an exterior wall with multiple outdoor units.
- Ducted and cassette systems are essentially larger scale variations on the same split design principle, just with the indoor unit hidden in a ceiling void or fitted flush into the ceiling itself rather than mounted visibly on a wall.
Why Are Split System Air Conditioners So Popular In The UK?
Split system air conditioners are popular in the UK because they combine strong energy efficiency with genuinely quiet operation, something older window units and basic portable air con simply can’t match.
Since the compressor, the noisiest component, sits outside in the condenser unit rather than inside your living space, indoor noise levels on premium models can drop as low as 18 to 19 decibels, barely noticeable during normal use.
Split systems from brands like Daikin, Mitsubishi Electric and Samsung also reach A+++ efficiency ratings, meaning lower running costs compared to less efficient alternatives, which matters given how much more common cooling demand has become across UK summers in recent years.
How Much Does A Split System Air Conditioner Cost To Install?
A split system air conditioner typically costs between £1,500 and £2,700 fully installed for a single room setup, rising to £2,800 to £7,000 for a multi split system covering several rooms, depending on brand, capacity and the complexity of the pipework run.
Running costs for a standard single room unit generally sit between 17p and 30p per hour, making day to day use considerably more affordable than many homeowners initially expect. Installation typically takes around a day for a single split system, though multi split setups covering multiple rooms can take a day or two longer depending on how far the pipework needs to run.
Do Split System Air Conditioners Need Regular Maintenance?
Split system air conditioners do need regular maintenance, with most manufacturers and installers recommending an annual service to keep the unit running efficiently and to protect any manufacturer warranty. A typical service includes checking refrigerant levels, cleaning or replacing filters, and inspecting both the indoor and outdoor units for any wear that could affect performance over time.
Skipping regular servicing is one of the most common reasons a split system loses efficiency over the years, so it’s worth booking annual maintenance through a certified engineer rather than waiting until a problem develops.
Get A Free Air Conditioning Installation Quote Today
Thinking about fitting a split system air conditioner in your home? Clever Energy Boilers provides expert air conditioning installation throughout the North West, Yorkshire and the Midlands, and our certified engineers can talk you through the right setup for your property. Request your free, no obligation air conditioning installation quote today.
FAQs
How long does a split system air conditioner typically last?
A well maintained split system air conditioner typically lasts between 15 and 20 years, provided it receives regular annual servicing and isn’t consistently run beyond its rated capacity.
Can a split system air conditioner be moved to a different room later on?
Moving a split system to a different room is possible but involves reinstalling both the indoor and outdoor units along with new pipework, making it a job for a certified engineer rather than a simple DIY relocation.
Does a split system air conditioner require a specific type of wall for installation?
Most external walls suitable for drilling a small hole for refrigerant pipework will work, though solid stone walls common in older Yorkshire properties may require additional planning, which is why console units are sometimes recommended as an alternative.
How far apart can the indoor and outdoor units of a split system be positioned?
Most residential split systems allow a maximum pipe run of around 15 to 20 metres between the indoor and outdoor units, giving reasonable flexibility for outdoor condenser placement.
Is a split system air conditioner louder than a central ducted system?
A split system’s indoor unit is generally no louder than a ducted system’s vents, since both keep the noisiest component, the compressor, located outside or in a hidden void away from living spaces.
