A split air conditioner is an air-to-air heat pump. Switch to heat mode and the same unit warms the room in winter.
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Standard or pre-charged systems
Yes, air conditioning can heat your home. A modern split system is an air-to-air heat pump: in heat mode it collects heat from the outside air and releases it indoors, giving several units of heat for each unit of electricity. It heats the rooms it serves rather than the whole house and does not make hot water.
In heat mode the system runs in reverse: the outdoor unit collects heat from the outside air, even on cold days.
The refrigerant carries that heat indoors.
The indoor unit releases it into the room as warm air.
Because it moves heat rather than making it, it delivers several units of heat for each unit of electricity used.
An inverter compressor speeds up and slows down to hold the temperature steadily.
Efficient electric heatingMoving heat is far more efficient than turning electricity straight into heat, as plug-in heaters do. Check each unit's seasonal heating efficiency (SCOP) in the quote.
Fast warm-upWarm air reaches the room quickly, which suits rooms you use at set times, such as a home office.
Rooms the boiler does not reachGarden rooms, extensions, lofts and conservatories without radiators.
Timers and app controlHeat a room before you need it, and only the rooms you are using.
| Air-to-air (air con) | Air-to-water | |
|---|---|---|
| Heats | Air in each room | Radiators or underfloor |
| Hot water | No | Yes, with a cylinder |
| Cooling | Yes | Usually no |
| Best for | Individual rooms | Whole-house heating |
Both types heat. A standard system gives more choice of sizes and multi-room options.
| Standard installed | Pre-charged | |
|---|---|---|
| F-Gas engineer needed | Yes | No, for a typical install |
| Electrician needed | Yes | Yes |
| Rooms per outdoor unit | One or several | One |
| Pipe run | Longer runs possible | Limited to the supplied kit unless a technician extends it |
| Indoor unit styles | Wall, floor, cassette, ducted | Mostly wall-mounted |
| Cooling and heating | Yes | Yes |
| Best for | Whole homes, larger rooms, businesses | One room where the outdoor unit can sit close by |
Home or business, how many rooms and the system type you would like.
Only installers who cover your postcode and fit your system type.
Weigh up prices, equipment and warranties, then choose, if you want to.
An air conditioner with an indoor unit in the room and an outdoor unit outside, joined by refrigerant pipes and a cable.
Units of cooling or heating output. 1 kW is about 3,412 BTU per hour. Units are sold in sizes such as 2.5 kW (9,000 BTU) and 3.5 kW (12,000 BTU).
A compressor that speeds up and slows down to hold the temperature, rather than switching fully on and off. Quieter and more efficient.
Seasonal efficiency ratings for cooling (SEER) and heating (SCOP). Higher numbers mean less electricity for the same comfort.
The qualification needed to install and work on equipment containing fluorinated refrigerants, which most standard systems use.
A split system sealed at the factory with a non-fluorinated refrigerant and a pre-flared pipe kit, so a typical install needs no F-Gas engineer.
One outdoor unit serving two or more indoor units in different rooms.
Water removed from the air while cooling, carried outside by a drain pipe or pump.
Another name for a reversible air conditioner: it moves heat from outside air into the room in winter.
Yes. Most split air conditioners are reversible heat pumps that heat as well as cool.
Usually, because it moves heat from outside rather than making it from electricity directly, giving several units of heat per unit of electricity. Running costs depend on your tariff, the unit and how you use it.
Yes, but output falls as temperatures drop. Check the rated heating output at low outdoor temperatures in the specification.
Not on its own for most homes. It heats air in the rooms it serves and does not make hot water. Many people use it alongside the boiler.
Enter your postcode, tell us about the rooms you want to heat and cool, and compare quotes from local installers.
General information only, not technical, legal or planning advice. Installers confirm system size, siting and any permissions for your property. Updated October 2026.
Sources: The Fluorinated Greenhouse Gases Regulations (GB) and GOV.UK guidance on F-gas; Approved Document P (electrical safety) and the Building Regulations for England and Wales; the Energy Performance of Buildings Regulations (air conditioning inspections); manufacturer installation guidance for split systems.