An air source heat pump is a heating system that takes heat from the outside air and transfers it into a property. Unlike a conventional boiler, which generates heat by burning fuel, an air source heat pump uses electricity to move available heat from the air into a building’s heating system.
Air source heat pumps are an important part of the renewable heating market in the UK and can provide heating and hot water when designed and installed as part of a suitable system.
What Is an Air Source Heat Pump?
An air source heat pump extracts thermal energy from the outdoor air, even when the weather is cold. The system then raises the temperature of this heat and transfers it into the property's heating system.
Depending on the system configuration, the heat can be used for:
- Space heating
- Domestic hot water
- Heating through suitable radiators or other heat emitters
The exact system design depends on the property, its heating requirements and the type of heat pump selected.
How Does an Air Source Heat Pump Work?
An air source heat pump works through a refrigeration cycle. The process involves several key stages that allow heat from outdoor air to be transferred into a property.
1. The Heat Pump Takes Heat From the Air
The outdoor unit draws air through the system. Although outdoor temperatures can be low, the air still contains thermal energy.
The heat pump uses a refrigerant to absorb this available heat.
2. The Refrigerant Absorbs the Heat
As the refrigerant absorbs heat from the outdoor air, it changes state. This allows the system to move the captured thermal energy through the heat pump.
3. The Compressor Raises the Temperature
The refrigerant gas passes through a compressor, which increases its pressure and temperature.
This raises the temperature of the refrigerant so that its heat can be transferred into the property's heating system.
4. Heat Is Transferred to the Property
The heated refrigerant passes through a heat exchanger. Heat is transferred from the refrigerant into the property's heating system.
This heat can then be used for space heating and, depending on the system, domestic hot water.
5. The Cycle Starts Again
After releasing its heat, the refrigerant cools and returns through the system. The cycle then repeats, allowing the heat pump to continuously transfer heat from the outdoor air.
What Can an Air Source Heat Pump Be Used For?
An air source heat pump can be designed to provide heating for a property and, depending on the system, hot water as well.
The exact configuration will depend on the heating requirements of the building.
A complete system may include an outdoor heat pump unit, controls, pipework, heat emitters and a hot water cylinder where required.
Air Source Heat Pump vs Boiler
The main difference between an air source heat pump and a conventional boiler is how heat is produced.
A boiler typically burns fuel to generate heat. An air source heat pump uses electricity to transfer heat from the outdoor air into the property.
This difference means that installing a heat pump requires consideration of the property's existing heating system and overall heat demand.
Factors such as insulation, heating emitters, flow temperature and hot water requirements can all be relevant when planning an air source heat pump installation.
Are Air Source Heat Pumps Efficient?
The efficiency of an air source heat pump depends on several factors.
These can include:
- Outdoor temperature
- Heat pump system design
- Flow temperature
- Property heat demand
- Insulation
- Heating controls
- Installation quality
Because heat pumps transfer heat rather than generating it through combustion, their performance depends on how the complete system is designed and operated.
For this reason, choosing an appropriate system for the property is an important part of an air source heat pump installation.
What Is Included in an Air Source Heat Pump System?
An air source heat pump system can consist of several components working together.
Depending on the installation, these may include:
- Outdoor air source heat pump unit
- Heating controls
- Hot water cylinder
- Pipework
- Heat emitters
- System controls and associated components
Not every property will require exactly the same configuration. The system should be designed around the property's heating and hot water requirements.
What Affects Air Source Heat Pump Running Costs?
Air source heat pump running costs can vary considerably between properties.
Factors that can affect running costs include the building's heat demand, insulation, system design, operating temperatures, electricity prices and how the heating system is used.
Therefore, there is no single running-cost figure that applies to every property.
If you are considering an air source heat pump, looking at the individual property's heating requirements and proposed system design is more useful than relying on a general estimate.
Is an Air Source Heat Pump Suitable for a UK Property?
Air source heat pumps can be used in UK properties, but suitability depends on the individual building and proposed heating system.
Before choosing a system, factors such as the property's heat demand, insulation, existing heating system, available outdoor space and hot water requirements should be considered.
The appropriate air source heat pump system should be selected based on the requirements of the property rather than using the same solution for every building.
Air Source Heat Pump Installation
Air source heat pump installation involves more than simply placing an outdoor unit outside the property.
The heating system needs to be considered as a whole. This can include heat demand, insulation, heating emitters, controls, hot water requirements and the type of heat pump system being installed.
A properly planned installation can help ensure that the selected system is appropriate for the property's requirements.
Why Consider an Air Source Heat Pump?
Air source heat pumps provide an alternative approach to conventional heating. They use electricity to transfer heat from the outside air and can provide heating and hot water as part of a suitable system.
For homeowners considering renewable heating, an air source heat pump is one technology worth exploring alongside other available heating options.
Frequently Asked Questions
How does an air source heat pump work?
An air source heat pump extracts heat from the outside air, increases its temperature through a refrigeration cycle and transfers the heat into the property's heating or hot water system.
Does an air source heat pump work in cold weather?
Yes. Air source heat pumps are designed to extract heat from outdoor air even when temperatures are low. Performance can vary depending on outdoor conditions and system design.
Does an air source heat pump provide hot water?
Yes, depending on the system configuration. An air source heat pump can provide heat for domestic hot water as well as space heating.
Does an air source heat pump use electricity?
Yes. Electricity powers the heat pump and allows it to transfer heat from the outdoor air into the property.
What affects air source heat pump efficiency?
Factors can include outdoor temperature, system design, flow temperature, property heat demand, insulation, heating controls and how the system is operated.
How much does an air source heat pump cost to run?
Running costs depend on factors such as heat demand, insulation, system design, electricity prices and how the heating system is used. There is no single figure that applies to every property.
Is an air source heat pump suitable for every property?
Not necessarily. Suitability depends on the building, heat demand, insulation, available outdoor space and requirements of the proposed heating system.