Glossary · Air conditioning
Air conditioning vs heat pump: what is the difference?
A reversible air conditioner is an air-to-air heat pump: it moves heat between the outdoor air and the room, cooling in summer and heating in winter. The difference people mean is usually air-to-air (warm air, no hot water) against air-to-water (heated water for radiators, underfloor heating and taps).
Key points
- Daikin says an air conditioner is also known as an air-to-air heat pump. Both move heat with a refrigeration cycle rather than making it by burning fuel.
- Air-to-air systems heat and cool the air in a room. Air-to-water systems heat water for radiators, underfloor heating and hot water.
- An air-to-air system does not connect to radiators and does not usually heat your hot water.
- The Boiler Upgrade Scheme lists £7,500 for an air source heat pump and £2,500 for an air-to-air heat pump.
- Refrigerant work needs a person holding the right F gas qualification.
How the two compare
Air conditioning and a heat pump work on the same principle. Daikin says an air conditioner is also known as an air-to-air heat pump, and that it is usually made of an indoor and an outdoor unit.[5]Daikin UK, Myth busting: Air conditioners In heating mode it absorbs energy from the outdoor air and releases it as heat through the indoor unit. In cooling mode the process is reversed.[5]Daikin UK, Myth busting: Air conditioners
So the useful question is which kind of heat pump you mean. Daikin describes two types of air source heat pump: air-to-air and air-to-water.[1]Daikin UK, Air source heating explained Air-to-air systems are also known as air conditioning and heat by blowing warm air into the home. Air-to-water systems heat water for radiators and underfloor heating, and they also supply hot water to taps.[1]Daikin UK, Air source heating explained
Air-to-air against air-to-water
| Air-to-air (air conditioning) | Air-to-water | |
|---|---|---|
| What it heats | The air in a room | Water for radiators, underfloor heating and taps |
| Cooling | Built in | Usually needs a separate system, Daikin says |
| Installation | Easier, mainly indoor and outdoor units | More complex, connects to plumbing |
| Hot water | Depends on the manufacturer | Standard feature |
| Radiators | Does not connect to them | Connects to radiators and underfloor heating |
The table follows Daikin’s comparison.[2]Daikin UK, How does a heat pump work? Daikin adds that an air-to-air system generally costs less to install because it does not need a water-based heating network, and that a separate domestic hot water system is usually needed.[1]Daikin UK, Air source heating explained For more, see air-to-air heat pump and air-to-water heat pump.
Grants and fitting
The Boiler Upgrade Scheme lists £7,500 towards an air source (air-to-water) heat pump and £2,500 towards an air-to-air heat pump.[3]GOV.UK, Apply for the Boiler Upgrade Scheme You must own the property and be replacing a fossil fuel heating system such as gas, oil, LPG or electric.[3]GOV.UK, Apply for the Boiler Upgrade Scheme The installer applies on your behalf. See boiler grants for how BASI handles this.
Either type contains refrigerant. GOV.UK says you must hold your own F gas qualification to install new air conditioning and heat pump systems, to service them and to check for leaks.[4]GOV.UK, Qualifications to work with F gas See refrigerant.
Example
Sunita wants cooling in her bedroom and living room in Bradford and some extra winter heat in the same two rooms. Her gas central heating stays. A split or multi-split air conditioner does that without touching her radiators. If she wanted to replace the gas boiler and heat the whole house, she would be looking at an air-to-water heat pump instead, and the grant would be a different amount.[3]GOV.UK, Apply for the Boiler Upgrade Scheme
What people get wrong
The biggest mix-up is expecting an air conditioner to replace a boiler. An air-to-air system heats rooms directly. Daikin says it does not integrate with radiators and does not heat water for a wet central heating system.
That comes from Daikin’s guide to air source heating.[1]Daikin UK, Air source heating explained
The second is assuming it is just cooling. Daikin says air conditioners heat and cool by transferring energy, so the unit can run all year.[5]Daikin UK, Myth busting: Air conditioners The efficiency ratings differ for each mode: SEER for cooling and SCOP for heating.
The bottom line
A reversible air conditioner is an air-to-air heat pump. The real choice is between air-to-air, which heats and cools rooms by moving air, and air-to-water, which heats water for radiators, underfloor heating and taps. Pick by what you need to replace, check which grant applies, and use an installer with the right F gas qualification.
Common questions
Is an air conditioner the same as a heat pump?
A reversible one is. Daikin says an air conditioner is also known as an air-to-air heat pump. It cools in summer and, by reversing the cycle, takes heat from outside air to warm the room in winter.
Can an air-to-air heat pump heat my radiators?
No. Daikin says an air-to-air heat pump does not integrate with radiators. It heats and circulates air directly into a room. An air-to-water heat pump is the type that feeds radiators and underfloor heating.
Can I get a government grant for air conditioning?
The Boiler Upgrade Scheme page lists £2,500 towards an air-to-air heat pump, alongside £7,500 for an air source or ground source heat pump. You must own the property and be replacing a fossil fuel heating system.
Do air conditioning units need a qualified installer?
Yes for the refrigerant side. GOV.UK says you must hold your own F gas qualification to install, service or check for leaks on air conditioning and heat pump systems, and it is against the law not to.
Sources
We cite the original source for every figure: government, regulators, standards bodies and manufacturers' own documents. Each one shows the date we last checked it.
- Daikin UK. Air source heating explained. Checked 11 November 2026. ↩
- Daikin UK. How does a heat pump work?. Checked 11 November 2026. ↩
- GOV.UK. Apply for the Boiler Upgrade Scheme. Checked 11 November 2026. ↩
- GOV.UK. Qualifications to work with F gas. Checked 11 November 2026. ↩
- Daikin UK. Myth busting: Air conditioners. Checked 11 November 2026. ↩