Teaching installers about heat pump technology

The government has a target of 600,000 heat pump installations per year by 2028. However, with 28 million homes in the UK and just 72,000 installed in 2022, these targets will be difficult to reach with the current number of installers.

The Climate Change Committee states that the ‘Balanced Pathway’ to meet the Sixth Carbon Budget will require over 1 million heat pump installs per year from 2030, growing to 1.5 million per year by 2050. The Heat Pump Association suggested 50,200 installers will be needed by 2030 to deliver these numbers.

“Installers are integral to the UK’s transition to low-carbon heating,” says Paul Eveleigh, managing director of Kensa Heat Pumps. “Kensa is continually building a network of trusted, recommended and experienced installers across the UK to encourage and enable ground-source heat pump technology adoption for a green, and great, Britain.”

Air source vs ground source

Although ground-source heat pumps (GSHP) and air-source heat pumps (ASHP) work on similar principles, each have different efficiencies and capabilities due to their heat sources.

“An air-source heat pump works by extracting heat from the air outside and upgrading it so that it can be used to provide heating and hot water,” explains Russell Dean, residential product group director, Mitsubishi Electric. “They can do this even in outside temperatures as low as -20°C, meaning they are ideally suited to the British climate.”

As the name suggests, GSHPs harness heat energy from the ground, via buried pipework. In the UK, temperatures below ground remain fairly constant, between 10-12°C throughout the year, whereas air temperatures fluctuate. For example, during winter, with an external air temperature of 1°C, an ASHP will have to work harder to deliver water at 50°C through a property’s radiators than a GSHP harnessing a ground temperature of 10°C.

However, GSHPs require boreholes to lay the network of pipes needed to absorb heat from the ground, and this can increase installation costs when compared to an ASHP, which only needs a small amount of outside space for the unit.

“While both types offer much higher rates of efficiency than a traditional gas boiler, it’s important to consider your building’s specific requirements, such as size, the amount of space available and the number of occupants, as this can dictate which type of heat pump is the most suitable,” says Dean.

“There are also water-source heat pump systems that can now extract energy from a water loop within a building using fifth-generation heat networks, with ultra-low temperatures of between 10-30°C. These systems upgrade the water temperature to deliver heating and hot water for individual apartments, while reducing distribution losses and overheating, which can occur with current heat networks.”

Heat pumps are suitable for both residential and commercial buildings, where demand for hot water fluctuates throughout the day, because they can operate at high temperatures of up to 90°C, according to Mitsubishi Electric.

“As well as heating buildings of all sizes and ages, GSHP can also deliver active or passive cooling,” points out Eveleigh. “It can be as smart or as simple as required – integrating with controls or other renewable technologies to provide low-cost and low-maintenance heating.”

A ground-source heat pump can deliver 3–4 kilowatts (kW) of heat for every 1 kW of electricity it consumes. Using freely available heat energy from the ground, it achieves higher efficiencies than any other heating system. This means it has the ability to reduce a property’s heating costs by around two-thirds compared to direct electric heating.


Ground- and air-source heat pumps have a lower flow temperature than other heating devices, like boilers, as they produce heat in a completely different way. This may mean that they will require larger surface areas, such as underfloor heating or bigger radiators, to reach a building’s required temperature quicker. For example, a room that needs 500W can be heated just as quickly by a larger radiator operating at 50°C as by a small radiator operating at 70°C.

“Selecting whether to have underfloor heating or radiators and what floor covering to use can all affect the efficiency of the ground-source heat pump system, which ultimately impacts fuel bills,” explains Eveleigh. “Typically, well-insulated homes with underfloor heating downstairs and radiators upstairs (oversized if a renovation) return the best results.”

It’s rare for properties to require a completely new radiator system as existing radiators can be used in other places. For example, the living room radiator could be moved to the bedroom and replaced with a new larger one. Typically, radiators need replacing every 15–20 years, and the cost differential to upsize them for a lower flow temperature of 50°C is minimal.

Water storage

A common misconception about heat pumps is that they require a buffer tank. However, according to Kensa, it is often possible to use the heating distribution system itself as the buffer, assuming that a number of zones or radiators can be left permanently open and uncontrolled, with the minimum flow and volume requirements met by the system itself.

“Some systems will need a separate, smaller storage tank known as a buffer tank,” explains Eveleigh. “You can often avoid this by using a few open zones and ample pipe sizes. The heat pump manufacturer should again be able to provide you with guidance on the minimum flow rates and the minimum volume of water in the circuit, but don’t be tempted to try and use a thermal store to provide buffering.

“Hot water systems are usually very similar to a common Y-plan design, with a separate hot water cylinder, although the three-port valve will not have a mid-position in operation,” explains Eveleigh. “Getting good domestic hot water performance relies on having matched components. The internal diameter of the coil within a cylinder affects the flow rate; this is just as important as getting the surface area of the coil right.

“Thermal stores can be very difficult to set up and get working well with a heat pump, which is mostly due to the lower operating temperature compared to a boiler. The simple solution is to use a cylinder approved by the ground-source heat pump manufacturer.”

Certified products

The Microgeneration Certification Scheme (MCS) is an accreditation process for renewable technologies. At present, every heat pump installation must be accredited under the MCS scheme for the installation to be eligible for grant funding and financial support schemes like the Boiler Upgrade Scheme or Home Energy Scotland.

“Kensa’s MCS Umbrella supports installers to ensure projects meet MCS standards, removing workload and providing useful learning opportunities,” explains Eveleigh. “During the process, Kensa takes full MCS responsibility for the sizing, specification, appropriate quotation, commissioning and MCS registration of domestic installations. The MCS Umbrella Service provides a helping hand for installers and reassurance for homeowners that their installations meet MCS standards.”

A Mitsubishi control unit

Financial support

Often thought to be an expensive alternative to boilers, heat pumps actually cost less to install than people may think and offer reduced running costs when compared to traditional heating systems.

“With 0% VAT for eligible domestic properties, alongside either a £7,500 grant from the Boiler Upgrade Scheme in England and Wales, or up to a £9,000 grant from Home Energy Scotland (the higher amount being for households that qualify for a rural uplift to cover the increased costs of necessary home improvements), these grants are designed to offset the cost of installation,” says Eveleigh. “Additional funding can be requested as an optional interest-free loan.”

MCS-certified installers can redeem the Boiler Upgrade Scheme (BUS) voucher, confirm proof of the installation and process the completed paperwork. Installers are responsible for ensuring that the value of the grant funding is passed on to the property owner to reduce the cost of the overall heat-pump system installation.

“Heat pumps deliver hot water in an incredibly efficient way,” says Dean. “Data shows they can provide at least three times more energy than they consume. They are the most viable alternative to traditional gas boilers as they can be installed in all types of homes and businesses to provide all the heating and hot water required.”

Accredited training

Demand for low-carbon heating systems is expected to increase over the coming year, with the recent amendments of Part L of the Building Regulations, as well as the planned introduction of a Future Homes Standard in 2025. According to the (MCS), it has certified 4,400 contractors to provide heat pumps in the UK, which falls short of an estimated 30,000 engineers that the CIPHE expects will be needed to meet government targets in the next four years.

“Effective training for the design and installation of low-carbon heating systems is of vital importance to deliver on government aims for a minimum of 600,000 heat pumps to be installed annually in the UK from 2028,” says Kevin Wellman, CEO of the CIPHE.

The CIPHE, the Heat Pump Association, LCL Awards, manufacturers and industry professionals, have collaborated to develop the Ofqual-accredited Low Temperature Heating and Hot Water Systems in Dwellings qualification.

“The qualification is ideal for plumbing and heating engineers who want to continue their professional development and help the industry meet demand for renewable heat installers,” says Wellman.

Heat pump deployment

Recognising that the heating sector contributes nearly one-third of the country’s carbon emissions, the government has outlined a vision to install 600,000 heat pumps annually by 2028. However, a recent report from the Heat Pump Association (HPA) sheds light on the current challenges, revealing that the existing market size is only 10% of the 2028 target.

“As the UK endeavours to decarbonise over 30 million homes and businesses within 25 years, heat pumps emerge as a leading solution,” says Charlotte Lee, CEO of the Heat Pump Association (HPA). “Offering efficiency rates over three times higher than fossil fuel boilers, heat pumps have the potential to reduce heating emissions by up to 75%. The HPA’s analysis of the Marginal Abatement Cost underscores that heat pumps represent the most scalable and cost-effective option for decarbonising heat in UK buildings. However, realising this potential requires swift and comprehensive policy interventions.”

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