Heat pumps are becoming a more familiar alternative to gas boilers, but the type most commonly installed in UK homes isn’t the only option.Homeowners in England and Wales can now get £2,500 towards the cost of an air-to-air heat pump through the government’s Boiler Upgrade Scheme (BUS). These systems work differently from the air-to-water heat pumps typically used to replace a boiler, and could be particularly well suited to smaller homes and flats.The new support sits alongside the existing £7,500 grants for air-to-water and ground source heat pumps. There is also currently a higher £9,000 grant for eligible homes that use oil or LPG and aren’t connected to the gas grid, which is available until 31 March 2027. So, what exactly is an air-to-air heat pump, and could the £2,500 grant make one worth considering?What is an air-to-air heat pump?Like other heat pumps, an air-to-air system takes heat from the outside air and transfers it into your home. The difference is what happens next.An air-to-water heat pump uses that energy to heat water, which is then circulated around radiators or underfloor heating. An air-to-air heat pump warms the air directly, usually distributing it through wall-, floor- or ceiling-mounted indoor units.In practical terms, the technology is closely related to air conditioning. Most systems can reverse direction during warmer weather, taking heat from inside your home and moving it outdoors instead. That means one installation can potentially provide both heating in winter and cooling in summer. The trade-off is that most air-to-air systems don’t provide domestic hot water. You’ll therefore need another way to heat water for showers, baths and taps, such as an immersion heater or another dedicated hot-water system.How much does an air-to-air heat pump cost?Air-to-air systems can be considerably cheaper to install than the air-to-water heat pumps more commonly used as boiler replacements.Energy Saving Trust research puts the typical cost at around £1,900 for a system heating a single room and approximately £3,700 for a three-bedroom semi-detached home.Those figures should only be treated as a guide, though. To qualify for the Boiler Upgrade Scheme, a heat pump must be sized to meet the full space-heating requirements of your property, so the price of a grant-eligible installation will depend on the size and layout of your home, how many indoor units you need and the complexity of the work.However, with £2,500 now available towards an eligible installation, air-to-air could become a significantly more affordable route into heat-pump heating for some households.Who are air-to-air heat pumps best suited to?One of the biggest advantages of air-to-air systems is that they don’t require a wet central-heating system.That could make them particularly interesting for flats and smaller properties, as well as homes that are currently being heated by electric panel heaters or storage heaters where installing new pipework, radiators and a hot-water cylinder could be costly or disruptive.They may also appeal if summer overheating is becoming a problem. Unlike a conventional boiler replacement, an air-to-air heat pump can generally provide effective cooling as well as heating.However, they won’t suit every property. Larger homes may require several indoor units, while homeowners who already have an effective radiator system may find an air-to-water heat pump offers a more straightforward way of replacing their boiler while continuing to provide both heating and hot water.The appearance of indoor units is another consideration, particularly if several rooms need to be heated.Can I get the £2,500 Boiler Upgrade Scheme grant?The £2,500 air-to-air grant is available for eligible residential properties in England and Wales.As with other BUS grants, the system must replace an existing fossil-fuel or electric heating system rather than another low-carbon heating system. The heat pump must meet the scheme’s technical requirements and be installed by an installer certified under the Microgeneration Certification Scheme (MCS).You don’t normally apply to Ofgem yourself to get the grant. The scheme is installer-led, which means your installer makes the application and the £2,500 should appear as an upfront discount on your quote.For the full eligibility requirements and details of how the process works, see our guide to the Boiler Upgrade Scheme. How can Octopus help with air-to-air heat pumps?Octopus Energy already installs air-to-water heat pumps, but homeowners interested specifically in air-to-air systems can also explore them through its Octopus Trusted Partner network.Octopus can connect customers with independent companies that offer air conditioning and air-to-air heat pumps. According to Octopus, these partners are selected, vetted and monitored against its standards for safety, quality and customer service.The partner then deals directly with the homeowner for the survey, quote, installation and ongoing support.For some households, an air-to-air heat pump won’t be a direct substitute for their existing boiler, but for smaller properties, homes without wet central heating or those that would also benefit from summer cooling, the combination of lower installation costs and the new £2,500 grant makes them an option that is increasingly worth considering.