Air-to-Air vs Air-to-Water: Which Heat Pump Do You Need?
Both are heat pumps, both are efficient, but they do quite different jobs. Choosing between an air-to-air system (air conditioning) and an air-to-water system comes down to whether you want cooling, central heating, or both. Here is a straight, honest comparison — including the grant point that often decides it.
In short
Air-to-air heat pumps (air conditioning) deliver warm or cool air to rooms and both heat and cool. Air-to-water heat pumps heat water for radiators, underfloor heating and hot water but do not cool. Only air-to-water qualifies for the Boiler Upgrade Scheme grant; air-to-air does not.
What each system does
An air-to-air heat pump is what most people call air conditioning. An outdoor unit feeds one or more indoor units that blow conditioned air into your rooms. It cools in summer and heats in winter, responds within minutes and needs no water pipework, so installation is quicker and less disruptive.
An air-to-water heat pump takes heat from the outside air and uses it to warm water, which then circulates through radiators or underfloor heating and fills your hot-water cylinder. It is designed to replace a gas or oil boiler. It does not provide cooling.
The grant question — stated accurately
This is the difference that often settles the decision. The Government's Boiler Upgrade Scheme (BUS) offers a grant towards low-carbon heating, and air-to-water heat pumps are eligible (subject to property and EPC conditions). Ground-source and biomass also qualify.
Air-to-air heat pumps (air conditioning) are not currently eligible for the BUS grant. We are clear about this because it is the single most misunderstood point in the market. If a quote promises a government grant on air conditioning, treat it with caution — the funding is for water-based and ground-source systems only.
So which should you choose?
Choose air-to-air if cooling matters to you (or you want both cooling and efficient room heating), you want a faster, tidier install, and you are not trying to rip out your central heating. It is the practical pick for comfort in a warming South-East climate.
Choose air-to-water if your goal is to decarbonise your heating, replace a boiler and heat hot water, and benefit from the BUS grant. Some homeowners sensibly do both — air-to-water for heating, air-to-air for summer cooling. We will give you an honest steer for your property and budget.
Air-to-air vs air-to-water heat pump comparison
| Factor | Air-to-air (air conditioning) | Air-to-water |
|---|---|---|
| Cooling | Yes | No |
| Space heating | Yes (warm air to rooms) | Yes (radiators / underfloor) |
| Hot water | No | Yes |
| Replaces a boiler | No | Yes |
| Distribution | Refrigerant to indoor air units | Water pipework |
| Install disruption | Lower, no wet pipework | Higher, plumbing involved |
| BUS grant eligible | No | Yes (subject to status) |
Frequently asked questions
Can air-to-air heat pumps get the Boiler Upgrade Scheme grant?
Does an air-to-water heat pump provide cooling?
Can I have both an air-to-air and air-to-water system?
Which is cheaper to install?
Ready for a cooler home or office?
Book a free, no-obligation survey and fixed quote with Guildford’s air conditioning specialists.