The truth about heat pumps

Luke Osborne Electrical Contractors Association

Heat pumps: dispelling the myths

The UK government sees heat pumps as a key low carbon energy technology, but they have come in for plenty of criticism. Luke Osborne explains how they work

It is essential that a heat pump is the correct size for its intended application

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s the UK continues to grapple with the effects of climate change and rising energy bills, heat pumps have emerged as one of the best ways to move away from high-emission fossil fuels and help reduce costs in the long run.

When it comes to decarbonising heat in our homes and offices, heat pumps provide a great solution. However, there are important points for installers, designers and facilities managers to bear in mind.

Building fabric

The fabric of a building should be the first call when considering how to reduce energy use. Energy use and running costs come down to how much thermal output the building requires. Ensuring that thermal losses are minimal will reduce both.

A full retrofit program will enable correct planning and co-ordination of works. For further information, see PAS 2035: Retrofitting Dwellings for Improved Energy Efficiency – Specification and Guidance.

Existing systems

Heat pumps operate at a lower temperature (under 55C) than conventional gas-fired wet heating systems. In homes with a condensing boiler system, the cost of this change should be relatively low. Older systems

which used hot water storage tanks and small emitters (operating at higher temperatures) may need both pipework and emitters changed to operate at the lower flow temperatures of heat pump installations.

Size

It is essential that a heat pump is the correct size for its intended application. Complete room-byroom heat-loss calculations will ensure correct sizing of emitters for each room. Designers and installers should calculate the total thermal demand and domestic hot water (DHW) to specify the size of the heat pump required. This saves the hassle of resolving inefficiencies caused by a heat pump that is too small, or even too large.

Efficient operation

To enable the efficient operation of a heat pump and to prevent excessive power cycling, designers should include a suitably sized thermal buffer within the system. This will ensure that the heat pump has sufficient heat to draw upon, without running constantly.

For the same reason, installers should put in a hot water cylinder for the DHW. These allow the heat pump to run ‘off-peak’ and also become active during demand side response (DSR), reducing the electrical load from the grid at times of peak demand. This benefits the end user, who can maximise time-of-use (ToU) tariffs, reducing running costs further.

Installation skills

We have seen some industry reticence in upskilling for heat pump installations, though the early adopters are taking a lead. As confidence increases, so will the installer base. With around a third of the UK population now considering heat pumps, more installers are looking to provide this service.

The early adopters are now creating career development pathways for both new entrants and those looking to upskill, with a growing number of courses available. Training providers may need assistance in ensuring there is sufficient access to courses across the UK.

Conventional heating is predominantly installed by heating engineers. However, as heat pumps are true M&E installations, electrical contractors are upskilling or partnering with heating engineers to offer a more complete service to their customers.

Future developments

Heat pumps are a proven technology that work well when sized and installed correctly in the right environment. Continental Europe has used heat pumps for decades. And the technology continues to evolve.

CO2 heat pumps have been available commercially for several years and some installers are trialling them in the domestic sector. A CO2 heat pump, which uses carbon dioxide as a refrigerant, can enable delivery of higher temperatures while also having a global warming potential (GWP) – the heat absorbed by any greenhouse gas in the atmosphere – of just 1. This compares very favourably to refrigerant gases used in other systems – for example, R410A has a GWP of some 2,088. ●

Luke Osborne is energy and emerging technologies solutions advisor at the Electrical Contractors Association.

Homeowners can claim £5,000 or £6,000 towards the installation of an air source heat pump (ASHP) or ground source heat pump (GSHP) respectively

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With around a third of the UK population now considering heat pumps, more installers are looking to provide this service

The cost to customers

With electricity (in normal times) being around three times the cost of gas per kWh, many consumers have asked about the economic viability of switching to heat pumps.

A well-designed and correctly sized heat pump should have an average seasonal coefficient of performance (ScoP) of between 3-4. This translates as 3-4kW of heat output for each kW used to run the heat pump. That means the running costs of a heat pump will be the same or less than a gas-fired system.

Through the Boiler Upgrade Scheme (BUS), homeowners in England and Wales can claim £5,000 or £6,000 towards the installation of an air source heat pump (ASHP) or ground source heat pump (GSHP) respectively.

For an ASHP installation this is a real help. A gas boiler replacement typically costs around £3,000, so this gives a homeowner a fund of £8,000 (as the homeowner would have been paying out £3,000 in any case). With ASHP installation costing between £7,000-£13,000, according to the Energy Saving Trust, this fund will cover all or a significant amount of the cost.

For most consumers, heat pumps are still an ‘unknown’ and there is much work required on messaging and educating the public. Installation horror stories tend to drown out the tens of thousands of successful installations around the country.