Air-to-air heat pumps extract heat from the outside air and transfer it to indoor air, and are a cost-effective and energy-efficient heating solution for homes and commercial buildings.
A 2024 report by the House of Commons shows that heating the UK’s 28 million homes accounts for 18% of all greenhouse gas emissions. Reducing emissions from heating is therefore central to reaching the government’s 2050 net-zero target.
This makes it necessary for households still relying on fossil-fuel systems, such as gas boilers, to begin switching to low-carbon alternatives. Among the most practical of these options are air-to-air heat pumps. Unlike conventional boilers that burn fuel, these systems move heat instead of producing it, making them highly efficient even during cooler months.
Air-to-air heat pumps are an appealing choice if you want to cut running costs while shrinking your carbon footprint. They offer both heating and cooling in one unit, require minimal maintenance, and are far easier to install than other heat pump types. With electricity now sourced increasingly from renewables, their environmental advantage continues to grow, turning what was once a niche technology into a mainstream solution for sustainable home comfort.
Key Takeaways on Air-to-Air Heat Pumps:
- Air-to-air heat pumps can cost from £1,900 to £3,700
- They’re very efficient and can produce 3–4 kWh of heat for every 1 kWh of electricity.
- They’re best for smaller properties like flats and park homes, and require good insulation and open-plan layouts
- They can help lower household heating emissions and energy costs
- Air-to-air heat pumps are not eligible for the Boiler Upgrade Scheme but benefit from 0% VAT on installation.
- They provide both heating and cooling in one system for all-year comfort.
How Do Air-to-Air Heat Pumps Work?
At its heart, an air-to-air heat pump operates on the same thermodynamic principles as a refrigerator, but in reverse. The process happens through something called the refrigeration cycle, a continuous four-step loop that transfers heat from outside to inside. Here’s the typical sequence:
Heat Absorption (Evaporation)
Cold outdoor air passes over the evaporator coil in the outdoor unit. The refrigerant inside the coil absorbs heat from the air and evaporates (turning from liquid to gas) even when outside temperatures are low.
This is possible because the refrigerant has a low boiling point, allowing it to extract thermal energy from ambient air.
Compression and Temperature Rise
The gaseous refrigerant enters the compressor, where its pressure is raised. That increase in pressure also raises its temperature substantially.
Heat Transfer Indoors (Condensation)
The hot, high-pressure gas flows to the indoor unit’s heat exchanger. There, as cooler indoor air blows over this coil (or via ducting), heat transfers from the refrigerant into the room air. The refrigerant condenses back into liquid as it gives up heat.
Expansion and Cooling of Refrigerant
The liquid refrigerant then passes through an expansion valve, dropping its pressure and temperature, readying it again to absorb heat from the outside. The cycle repeats.
It’s the same setup as an air conditioner. When cooling is desired, like in a hot summer, a reversing valve can flip the flow, allowing the system to extract indoor heat and expel it outdoors.
Costs and Installation in the UK
The cost of an air-to-air heat pump system depends on several factors, including home size, number of indoor units, and the overall complexity of the installation. According to the Energy Saving Trust, air source heat pumps cost around £11,000 while air-to-air models can range from £1,900 to £3,700.
Air-to-air heat pumps are generally less expensive than air-to-water models because it doesn’t connect to radiators or underfloor heating. Installation is also simpler and faster, often completed within one to two days. The installer mounts the outdoor unit on an exterior wall or ground bracket, connects refrigerant lines and electrical wiring, and then fits the indoor units in the chosen rooms.
Once connected, the system is vacuum-tested, charged with refrigerant, and commissioned to ensure proper airflow and efficiency. While upfront costs can seem significant, air-to-air heat pumps generally repay the investment through lower running expenses, reduced maintenance needs, and improved comfort across all seasons.
How Efficient Are Air-to-Air Heat Pumps?
Heat pumps are more efficient than traditional heating systems because they move heat instead of generating it. Government guidance notes that heat pumps can produce around three units of heat for every unit of electricity they use and significantly reduce a property’s energy demand when replacing technologies such as gas boilers.
The measure used to describe this efficiency is known as the Coefficient of Performance (CoP). A heat pump with a CoP of 3.0, for example, produces three units of heat for every single unit of electricity it consumes. Each manufacturer publishes the CoP for their model, based on laboratory test conditions that reflect mild outdoor temperatures.
In real-world use, however, efficiency varies with the weather. When temperatures drop in winter, the pump must work harder to extract heat, slightly lowering its CoP. To estimate running costs more accurately, manufacturers can also provide a Seasonal Coefficient of Performance (SCoP) or Seasonal Performance Factor (SPF), which shows the heat pump’s efficiency averaged across the whole year.
What are the Advantages of Air-to-Air Heat Pumps?
High Energy Efficiency
Air-to-air heat pumps can deliver three to four times more energy than they consume because they move heat instead of generating it. This results in lower energy use and reduced bills.
Reduces Carbon Footprints
Unlike gas and oil boilers, they’re a low-carbon heating system that takes heat from the outside air. They don’t produce emissions like systems powered by gas or oil, which helps improve your home’s carbon footprint.
Dual Heating and Cooling Function
Unlike traditional boilers, these systems work year-round. They heat during winter and act as air conditioners in summer, providing comfort in every season without needing a separate cooling unit.
Simple Installation
Air-to-air systems are easier to fit than air-to-water heat pumps because they don’t require plumbing connections. This makes them ideal for homes that rely on electricity or properties without access to mains gas.
Zoned Temperature Control
Many modern models allow different rooms or zones to be heated or cooled independently. This zoned control prevents wasted energy and keeps comfort levels balanced throughout the home.
What are the Disadvantages?
No Hot Water Supply
An air-to-air system cannot provide domestic hot water. Homeowners still need a separate system, such as an immersion heater or cylinder, for taps and showers.
Reduced Efficiency in Cold Weather
Performance naturally drops when outdoor temperatures fall below freezing, although modern models remain effective down to about −10 °C.
Visible Indoor Units
Some users prefer the look of traditional radiators. Wall-mounted fan units can be more visible, and while quiet, they may produce a soft background hum.
Outdoor Unit Placement
The external fan can produce mild noise, which might be noticeable if positioned close to bedrooms or outdoor seating areas.
Overall, when installed correctly in a well-insulated home, the benefits far outweigh the drawbacks. Air-to-air heat pumps remain one of the most practical and efficient ways to cut heating costs and carbon emissions in the UK.
Can You Use Government Grants for an Air-to-Air Heat Pump?
Unlike ground source and air source heat pumps, you can’t use government grants like the Boiler Upgrade Scheme (BUS) to purchase or install an air-to-air heat pump. The exclusion is due to their inability to produce hot water, as the BUS focuses on systems that replace both heating and hot-water supply.
However, there are still financial advantages available to households installing an air-to-air system. The government’s 0% VAT rate on energy-saving materials applies to heat pumps, reducing upfront installation costs by removing the 20% tax that would otherwise apply. Some households may also qualify for support through schemes that target energy-efficiency improvements for low-income and off-gas homes.
Even without a national grant, air-to-air heat pumps remain one of the lowest-cost renewable heating systems to install. Combined with their lower running costs and the increasing share of renewable electricity on the UK grid, they offer a financially sound route toward cutting energy bills and long-term carbon emissions.
Is Your Home Suitable?
Air-to-air heat pumps are usually installed in smaller properties like flats and park homes.
They perform best in homes that are well insulated and have an open-plan layout or large connected spaces where warm air can circulate freely. They’re particularly effective in properties that currently rely on electric heating and don’t have a gas supply because they provide a far more efficient alternative without major structural changes.
The system works by blowing warm air into living areas through one or more indoor units. For that reason, room layout matters. Homes with multiple small, enclosed rooms may need several fan units to ensure even heating throughout.
You must have somewhere suitable to put the air-to-air heat pump. You must position the outdoor unit in an area with good airflow, away from obstructions such as fencing or dense shrubs. Some emerging air-to-air systems can fit entirely inside the building, making them ideal for homes that have no room at all for an outside unit, such as a mid or top-floor flat.
Step-by-Step Installation Process
Installing an air-to-air heat pump is generally faster and less invasive than other types of heating systems. The process typically takes one to two days, depending on the number of indoor units and the complexity of the layout.
1. Initial Home Assessment
A qualified installer begins with a detailed site survey to determine heating requirements, room sizes, and optimal unit placement. This step ensures the system is correctly sized for the property and that airflow will be evenly distributed throughout the home. Oversized or undersized models can affect comfort levels and energy use. Proper insulation and draught-proofing are also essential; without them, heat will escape faster than the system can replace it, lowering efficiency.
2. Outdoor Unit Placement
The outdoor unit, which contains the compressor and heat exchanger, is mounted on an exterior wall or placed on a level surface just outside the property. It must have good ventilation and be positioned away from windows or outdoor seating areas to minimise noise.
3. Indoor Unit Installation
The indoor units are fitted to walls or ceilings in the chosen rooms. Each one connects to the outdoor unit via refrigerant pipes and electrical wiring, which are run neatly through small wall openings.
4. Electrical and Refrigerant Connections
Installers connect the system to the household’s power supply and vacuum-test the refrigerant lines to ensure no leaks are present. The system is then charged and sealed in accordance with F-Gas regulations.
5. System Testing and Commissioning
Once everything is in place, the installer runs the system to check airflow, temperature output, and pressure levels. The controls are programmed and demonstrated to the homeowner.
6. Registration and Warranty Activation
Finally, the installation is registered with both the manufacturer and, if applicable, a government-recognised certification body. This step ensures that the warranty and any potential VAT relief remain valid.
When installed by a certified professional, the process is quick, tidy, and minimally disruptive, giving homeowners a fully operational heating and cooling solution almost immediately.
How Do You Maintain A Heat Pump?
Air-to-air heat pumps require relatively little maintenance compared to traditional heating systems. Most of the work involves routine cleaning and occasional professional servicing to keep the system running efficiently.
You can easily maintain indoor units by vacuuming or rinsing air filters every few weeks to ensure steady airflow. Outdoor units should be kept free of leaves, dust, or snow buildup, which can restrict performance if airflow is blocked.
Professional servicing is usually recommended once a year, where an engineer checks refrigerant levels, electrical connections, and compressor performance. This ensures reliable operation and also preserves the manufacturer’s warranty.
Comparing Air-to-Air with Other Systems
Understanding how air-to-air heat pumps stack up against other heating options helps clarify when they’re the best choice and where their limitations lie.
Air-to-Air vs Air-to-Water Heat Pumps
Both are forms of air-source technology, but their output is different. Air-to-water systems heat water for radiators, underfloor circuits, and domestic hot water taps. Air-to-air systems, on the other hand, heat and cool the air directly through fan coils. This makes them quicker and simpler to install, with lower upfront costs and no plumbing work. However, they cannot supply hot water, so they’re best suited to homes that already have an electric or solar water heater.
Air-to-Air vs Ground-Source Heat Pumps
Ground-source heat pumps use buried loops to draw energy from the soil, delivering stable performance year-round. While this can mean slightly higher efficiency in cold conditions, installation costs are much higher because of the excavation required. Air-to-air systems are therefore far more affordable and flexible, especially for smaller properties or retrofits where ground loops aren’t feasible.
Air-to-Air vs Traditional Boilers
Unlike gas or oil boilers that burn fuel, air-to-air systems generate no on-site emissions and don’t rely on the gas grid. They’re cleaner, quieter, and safer, with no risk of carbon monoxide. Although boilers can still provide higher output temperatures, the running cost advantage of heat pumps, especially as the UK electricity mix becomes greener, continues to grow.
When all factors are considered, comparisons between air-to-air heat pumps vs gas boilers show they’re more efficient, low-maintenance, and ideal for properties ready to move away from fossil fuels without a complete system overhaul.
Best Air-to-Air Heat Pump Brands in the UK
Choosing the right brand plays a significant role in system performance, reliability, and long-term cost savings. The UK market offers several reputable manufacturers that have refined their air-to-air heat pump technology for efficiency, quiet operation, and durability. Below are some of the most trusted names and what sets them apart.
Daikin
Daikin remains one of the leading heat pump brands globally, known for its exceptional build quality and advanced inverter compressors. Its Perfera and Stylish ranges deliver high Seasonal Coefficients of Performance (SCOP) of up to 4.6, making them among the most efficient systems available. Daikin’s units are also praised for ultra-quiet operation and sleek indoor design options that fit modern interiors.
Mitsubishi Electric
The Mitsubishi Electric M Series is a strong choice for both small homes and larger properties. These systems are designed for UK conditions and maintain reliable heating performance down to –15 °C. They use a precision inverter system for steady temperature control and can connect to multiple indoor units, allowing easy zoning throughout the house.
Panasonic
Panasonic’s Etherea series offers impressive efficiency and air purification technology using nanoe™ X filtration. The combination of strong energy performance and improved indoor air quality makes these systems appealing for allergy-sensitive households. Their design is compact, easy to install, and ideal for retrofit applications.
LG
LG’s Artcool and Dual Inverter systems balance stylish design with smart functionality. With built-in Wi-Fi, app-based control, and low-noise operation, LG focuses on convenience and comfort. Their air-to-air units are also noted for reliability and affordability compared to some premium competitors.
Fujitsu
Fujitsu’s air-to-air heat pumps are widely used for their robust performance and straightforward controls. The KETA and ASYG series combine a SCOP of up to 4.3 with quiet, steady airflow. These systems are known for long service life and simple maintenance.
| Brand | Typical Output Range (kW) | SCOP Efficiency | Noise Level (Indoor / Outdoor) |
| Daikin | 2.5 – 7.1 | Up to 4.6 | 19 / 45 dB |
| Mitsubishi Electric | 2.0 – 6.1 | Up to 4.5 | 21 / 46 dB |
| Panasonic | 2.5 – 7.0 | Up to 4.4 | 20 / 43 dB |
| LG | 2.1 – 6.6 | Up to 4.2 | 19 / 44 dB |
| Fujitsu | 2.5 – 7.0 | Up to 4.3 | 22 / 46 dB |
Final Thoughts on Air-to-Air Heat Pumps
Switching to an air-to-air heat pump is one of the simplest ways to lower energy costs and reduce carbon emissions at home. With shorter installation times, all-season comfort, and proven long-term savings, the technology is quickly becoming a preferred choice for UK homeowners looking to future-proof their heating.
Before you decide, arrange a home energy survey to check your property’s suitability and get tailored recommendations. An installer can assess insulation levels, suggest the best system size, and estimate installation costs accurately.
If you’re upgrading from electric heating, the difference in comfort and efficiency will be immediate. Modern systems combine quiet operation with smart controls and cooling capability, transforming the way homes stay warm in winter and cool in summer.
FAQs on Air-to-Air Heat Pumps
What Are the Disadvantages of Air-to-Air Heat Pumps?
Air-to-air heat pumps cannot supply domestic hot water, so a separate system, such as a cylinder or immersion heater, is still required. Their efficiency also drops slightly in freezing weather, although modern systems remain effective down to around −10 °C. Some users may find the indoor wall units more visible than radiators, and outdoor fans can produce a soft hum if installed too close to windows or outdoor seating areas.
How Much Does It Cost to Install an Air-to-Air Heat Pump in the UK?
Unit costs can range from £1,900 to £3,700 and will increase depending on installation costs, property size, the number of indoor units, and system brand. Smaller flats or single-zone systems sit at the lower end of the range, while multi-room or premium systems reach the higher end. The process usually takes one to two days and must be carried out by a certified engineer to ensure safety and warranty compliance.
What Is the Downside to an Air-to-Air Heat Pump in the UK?
The main downside is that performance can vary with outdoor temperature. Efficiency naturally declines during freezing weather. Another limitation is that air-to-air systems only provide space heating and cooling, not hot water. In addition, installation requires outdoor space for the compressor unit, which isn’t ideal for every property type.
Are Air-to-Air Heat Pumps Worth It?
Yes, for many households, they are. Despite the upfront cost, air-to-air heat pumps can reduce heating bills, lower carbon emissions, provide cooling in summer, and require minimal maintenance. For well-insulated homes and properties off the gas grid, they are among the most cost-effective low-carbon heating options available.
Do You Need Radiators With an Air-to-Air Heat Pump?
No. Air-to-air systems don’t use radiators or pipes. They work by blowing warm air directly into rooms through wall-mounted or ceiling units. This setup provides quick, even heating without the need for a water-based system. Homes with existing radiators would only need them if switching to an air-to-water heat pump, which heats water rather than air.
What Is the Best Brand of Air-to-Air Heat Pump?
The UK’s top-rated brands include Daikin, Mitsubishi Electric, Panasonic, LG, and Fujitsu. Each is known for reliability, high energy efficiency, and quiet operation. Daikin and Mitsubishi Electric models are particularly popular for their strong performance in cold weather and sleek indoor design. Panasonic’s nanoe™ X technology adds advanced air purification for improved indoor air quality.
Sources and References
UK Parliament – Decarbonising home heating
Energy Saving Trust – Heat pumps: how they work, costs and savings
GOV.UK – Heat pumps explained: experts answer your questions
GOV.UK – Energy-saving materials and heating equipment (VAT Notice 708/6)