Air-to-air heat pumps transfer heat from the outside air to air inside your home, increasing the temperature of the air in each room. This warm air enters your home through a series of fan coil units, or ‘blowers’.
Air-to-air heat pumps are sometimes referred to as air conditioning. While many people think of air conditioning as a way of cooling buildings, it can also be used for heating.
An air-to-air heat pump does not heat water, so you will need to consider another way of heating water for showering, bathing and hot taps.
In the UK, air-to-air heat pumps are not typically used for heating larger homes, with most domestic air source heat pumps installations using air-to-water systems. More often, air-to-air heat pumps are installed in smaller properties, such as park homes or flats.
There are a few things to consider when deciding whether an air-to-air heat pump is right for you.
One advantage of an air-to-air heat pump is that it takes up little space. The fan coil units are wall mounted inside the house, with no floor standing equipment required.
You’ll need space outside your home for a unit to be fitted to a wall or placed on the ground. It will need plenty of space around it to get a good flow of air.
Most homes in the UK use radiators or underfloor heating to distribute heat to each room. An air-to-air heat pump uses fan coil units or blowers. Blowers are usually mounted high on the wall, which can be helpful where floor or lower wall space is limited. They can also be mounted at floor level or in the ceiling.
Air-to-air heat pumps can be single-head or multi-head – where ‘head’ refers to the number of blowers in use. Single-head air-to-air heat pumps have a single heat capture unit outside and a single blower inside. Multi-head air-to-air heat pumps have a single heat capture unit outside and multiple blowers inside.
Generally, single-head air-to-air heat pumps are only suitable in the smallest homes, or for single room heating. If you have more than two rooms, it is likely you will need a multi-head air-to-air heat pump.
Having a single-head blower against an outside wall and next to the outside heat capture unit means you need less piping or ducting, which can lead to quicker and cheaper installation. Multi-head installations need to have pipes or ducts travelling from the outside heat capture unit to each blower – just as boilers need pipes running to a radiator in each room. Multi-head installations are more complex, and typically more expensive and disruptive to install.
If your home is already built, it can be challenging to design ducts to connect each room’s blower to the outdoor heat capture unit unobtrusively. For this reason, blowers are often installed on the inside of an exterior wall, to reduce the length of pipes required internally. If your home doesn’t already have ducts, and you’re planning to install a multi-head system, the new ducting installed will be visible in each room, or will need to be boxed in. Luckily, it is usually possible to do this without too much visual impact.
Air-to-air heat pumps don’t heat water so you will need another way of heating water for showering, bathing and hot taps. There are several options, and what’s best for you will depend on the amount of hot water your household needs, as well as any space or budget considerations.
You could consider a hot water cylinder fitted with an electric immersion heater, or if you don’t use much hot water, you might consider using direct electric showers and a small, instantaneous water heater fitted under your sink. Other options include a boiler or solar water heating.
Running costs will depend on how your heat pump is designed and how it is operated. Savings on your energy bill will also be affected by the system you are replacing.
There is currently very little independent data on how air-to-air systems perform in the UK, so it’s difficult to predict how much money you would save by fitting one. However, we can give some general guidance on what to expect.
Saving money on fuel bills isn’t everyone’s primary motivation for installing a new heating system, but you need to be sure you can afford to run the system once installed. You should ask your installer for an indication of running costs based on their design of the system for your home.