Air Con vs Air-to-Air Heat Pump: Which Should You Choose?

An air conditioner and an air-to-air heat pump are, in almost every case sold in the UK today, the same machine. Both use a compressor, a refrigerant circuit and a reversing valve. What differs is certification, not hardware, and that difference decides whether you can claim the £2,500 government grant or need planning permission. If you have been going round in circles trying to understand this air con vs air-to-air heat pump question, that is the whole answer. What follows is which situation applies to you and what to do about it.

What is the actual difference between air conditioning and an air-to-air heat pump?

Strip away the marketing and there is very little difference to find. A standard split system air conditioner and an air-to-air heat pump both work by moving heat rather than generating it, using a compressor and a refrigerant circuit to shift warm air out of a room in summer. The part that turns a cooling-only unit into a heat pump is a reversing valve, a component that lets the system run the same process backwards and pump heat into the room instead of out of it.

Almost every modern split system sold in the UK already has this valve fitted. So in practice, the question is rarely which machine to buy. It is how the installer certifies and registers what they have installed.

The two versions of the same machine

A cooling-only unit, sold and installed simply as air conditioning, is not MCS certified as a heat pump even if the hardware inside it is capable of heating. It cannot access Class G permitted development rights, and it cannot claim the £2,500 Boiler Upgrade Scheme grant.

A unit with the same reversing valve, installed by an MCS-certified installer and registered as an air-to-air heat pump providing both heating and cooling, can access Class G permitted development for most homes and may qualify for the £2,500 grant, subject to the conditions below.

Which is right for your situation?

You have a working gas boiler and just want cooler bedrooms in summer

This is the most common reason people land on this page. If your boiler is staying and you simply want a system to cool one or two rooms, you do not need to chase heat pump certification for its own sake. Your installer can quote you as standard air conditioning. You will not clearly qualify for the BUS grant in this scenario, because the grant is designed for households replacing their heating system, not adding a supplementary cooling unit. More on that below.

You are thinking about replacing your heating system

If your boiler is ageing and you are weighing up whether to replace it with something that heats and cools, this is where the certification genuinely matters. Ask your installer to quote the same hardware as an MCS-certified air-to-air heat pump. The certification cost is usually £200 to £500 more than a cooling-only quote (approximate, based on Q2 2026 industry pricing), but the £2,500 grant, if you qualify, comfortably covers that difference and leaves you ahead.

The BUS grant: who qualifies and who does not

The £2,500 Boiler Upgrade Scheme grant for air-to-air heat pumps has been live since 28 April 2026. Source: gov.uk and Ofgem.

To qualify, all of the following generally need to be true:

• The property is in England or Wales.
• The new system replaces an existing fossil fuel or electric heating system, not supplements one.
• The installer is MCS certified.
• The property is residential. Non-residential properties are explicitly excluded for air-to-air systems.
• A valid EPC is used as evidence where one exists.

For the full eligibility detail, including what counts as a qualifying replacement, see our air-to-air heat pump grant guide.

Planning permission: why certification matters

A cooling-only air conditioning unit does not qualify for Class G permitted development rights, because those rights are reserved for systems that provide a heating function. That can mean applying for planning permission for something as ordinary as an outdoor condenser unit, depending on your property and local authority.

An MCS-certified air-to-air heat pump, because it heats as well as cools, is Class G permitted development eligible for most homes, subject to standard conditions such as unit size and distance from a boundary. This is a second, separate reason some buyers choose heat pump certification even when their main interest is cooling.

What to ask your installer

Whichever situation you are in, ask these questions before you sign anything:

• Is this being quoted as standard air conditioning or as an MCS-certified air-to-air heat pump, and what does that change about the price?
• Am I replacing my existing heating system or adding a supplementary cooling system, and does that affect BUS grant eligibility in my case?
• Does this installation qualify for Class G permitted development, or will I need to apply for planning permission?
• What is the running cost difference in heating mode compared with my current boiler, based on current Ofgem rates rather than an old estimate?

On that last point, the current Direct Debit electricity price cap rate is 26.11p per kWh for 1 July to 30 September 2026 (Ofgem, confirmed 27 May 2026). A heat pump typically delivers 3 to 4 units of heat for every unit of electricity it uses, which is what makes the heating side worthwhile even at current electricity prices. Ask your installer to run the comparison against your actual gas usage rather than relying on a generic figure.

Bottom line

If you are only after summer cooling and your boiler is staying, book standard air conditioning and do not expect the grant. If you are open to replacing your heating system, ask specifically for an MCS-certified air-to-air heat pump quote and get your installer to confirm BUS eligibility in writing before you commit. Same machine either way. The certification is the only thing that changes what you are entitled to.

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