What is an Air Source Heat Pump?

What Is an Air Source Heat Pump?

As the UK and Ireland move towards lower-carbon, more energy-efficient homes, air source heat pumps are becoming an increasingly popular option for home heating and hot water.

But what exactly is an air source heat pump, how does it work, and could one be suitable for your home?

BPC Ventilation supplies air source heat pumps and supporting heating components for new builds, renovations and home heating upgrades. Here’s a simple guide to how they work and what you should consider before choosing one.

How Does an Air Source Heat Pump Work?

An air source heat pump (ASHP) extracts thermal energy from the outside air and transfers it into your home.

Even when the outdoor temperature is low, there is still heat energy available in the air for the system to extract.

The process works in several stages:

The outdoor unit absorbs heat from the outside air using a refrigerant.
The refrigerant passes through a compressor, increasing its pressure and temperature.
The captured heat is transferred into the home’s heating system.
With an air-to-water heat pump, this heated water can then supply radiators, underfloor heating and, when correctly designed, domestic hot water.

A simple way to think about it is like a refrigerator operating in reverse. A fridge moves heat from inside the appliance to the room around it, while a heat pump transfers heat from outside into the property.

What Are the Benefits of Air Source Heat Pumps?

Energy-Efficient Heating

Air source heat pumps transfer heat rather than generating it through direct combustion.

Under suitable operating conditions, a heat pump can deliver several units of heat for each unit of electricity consumed. Actual efficiency will vary depending on outdoor temperature, flow temperature, property heat loss and system design.

Lower-Carbon Heating

Heat pumps provide an alternative to heating systems that directly burn fossil fuels such as oil or gas.

The carbon impact of the system will depend on factors including electricity generation, system efficiency and how the property is heated.

Ideal for Low-Temperature Heating

Heat pumps generally operate more efficiently when the heating system can run at lower flow temperatures.

This makes them particularly well suited to water underfloor heating and correctly sized low-temperature radiators.

Heating and Hot Water

Air-to-water heat pumps can provide space heating and can also be incorporated into a domestic hot water system when paired with a suitable cylinder and controls.

BPC Ventilation's air source heat pump range includes heat pumps alongside cylinders, buffer tanks, controls and supporting system components.

Cooling with Suitable Systems

Some heat pump systems can also provide cooling when the equipment, emitters and controls have been designed to support it.

Cooling capability varies by heat pump model and system configuration, so it should be considered during the design stage rather than assumed to be available on every installation.

Are Air Source Heat Pumps Suitable for Older Homes?

Air source heat pumps aren't limited to new-build properties.

They can also be considered for older homes and renovation projects, but the property needs to be assessed carefully.

Important factors include:

Wall, roof and floor insulation
Window and door performance
Overall property heat loss
Existing radiators or underfloor heating
Available outdoor space
Required flow temperature
Domestic hot water requirements
Electrical supply

A well-insulated property will generally require less heating energy, which can make it easier for a heat pump to maintain comfortable temperatures efficiently.

However, property age alone does not determine whether a heat pump is suitable. The condition and performance of the building should be considered as part of the system design.

Air Source Heat Pumps and Underfloor Heating

One of the most popular combinations is an air source heat pump paired with water underfloor heating.

Underfloor heating distributes warmth across a large floor surface rather than relying on smaller wall-mounted emitters.

This allows a correctly designed UFH system to deliver useful room heat output at relatively low water temperatures, which can complement the operating characteristics of a heat pump.

When planning both systems, factors including room heat loss, UFH pipe spacing, required flow temperature and heat pump output should ideally be considered together.

Can You Use an Air Source Heat Pump with Radiators?

Yes, air source heat pumps can be used with radiators, but the radiators need to be capable of providing enough heat at the proposed water temperatures.

Radiators originally selected for a traditional boiler may have been designed around much higher flow temperatures.

At lower temperatures, the same radiator will provide less heat output. This means some properties may require larger radiators or alternative low-temperature emitters when changing to a heat pump.

A proper heat-loss and emitter assessment can help determine whether existing radiators are suitable.

How Do You Choose the Right Size Heat Pump?

Heat pump sizing should not be based solely on the floor area or number of bedrooms in a property.

A suitable specification should consider factors such as:

Whole-property heat loss
Room-by-room heating demand
Insulation and airtightness
Outdoor design temperature
Radiator or UFH output
Required flow temperature
Domestic hot water demand

An undersized heat pump may struggle to meet the heating demand during colder conditions, while unnecessarily oversizing equipment can also affect system operation.

BPC Ventilation's heating team can provide support when selecting suitable heat pump equipment and supporting components for a project.

What Brands of Air Source Heat Pumps Does BPC Ventilation Supply?

BPC Ventilation's current air source heat pump range includes equipment from established manufacturers including Mitsubishi and Panasonic.

Different heat pump outputs and configurations are available, allowing equipment to be selected around the requirements of different properties and heating systems.

The range also includes supporting products such as:

Hot water cylinders
Buffer tanks
Thermostats and controls
Temperature sensors
Connection components
Other heat pump accessories

How Much Does an Air Source Heat Pump Cost to Run?

There isn't one running-cost figure that applies to every property.

Actual energy use will depend on factors including:

The property's heat loss
Outdoor temperatures
Electricity prices
Required flow temperature
Heat pump efficiency
Heating schedules and controls
Hot water demand
How well the overall system has been designed

This is why system design matters just as much as the heat pump itself.

A heat pump operating at unnecessarily high flow temperatures or connected to unsuitable emitters may use more electricity than the same unit operating within a properly designed low-temperature system.

Are Grants Available for Air Source Heat Pumps?

Financial support may be available depending on where the property is located and the current eligibility rules.

For example, eligible property owners in England and Wales may be able to receive support through the Boiler Upgrade Scheme.

Grant values and eligibility requirements can change, so always check the latest government guidance before making purchasing or installation decisions based on available funding.

Is an Air Source Heat Pump Right for Your Home?

An air source heat pump can be worth considering if you're:

Building a new home
Planning a major renovation
Replacing an older heating system
Installing underfloor heating
Looking for an alternative to oil or gas heating
Designing a low-temperature heating system

However, every property is different. Insulation, heat loss, emitters, hot water demand and the overall system design should all be considered before equipment is selected.

Get Help Choosing an Air Source Heat Pump

BPC Ventilation supplies air source heat pumps and supporting heating products for new builds, renovations and home heating upgrades.

The BPC heating team can provide support with product selection and the wider system components required for your project, including underfloor heating, cylinders, buffer tanks and controls.