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Electrification of Heat Demonstration Project
Case study

Carole and Kelvin’s hybrid heat pump

“We used to have cold spots in the house. Now it’s brilliant!”

The project

Funded by the UK Government Department for Business, Energy and Industrial Strategy , the Electrification of Heat Demonstration Project was designed to understand the technical and practical feasibility of a large-scale rollout of heat pumps. Find out more about the project.

Carole and Kelvin were part of the project.

The challenge

It was about time for Carole and Kelvin to replace their old gas boiler. It often broke down and they knew that, due to its age, spare parts would soon be less easy to find. In addition, they found that the warmth and comfort in the house was inadequate. 

“The hallway used to be very cold and the utility room was an icebox as the radiator there was too small.”

The UK Government funded Electrification of Heat Demonstration Project, which is trialling heat pumps, gave them the opportunity to use a more sustainable energy technology to upgrade their heating system. As they are both environmentally aware, Carole and Kelvin were pleased to install a heating system which would provide a more environmentally responsible solution for the long term. 

Solution and benefits

A hybrid heat pump system was installed at Carole and Kelvin’s house. This uses an air source heat pump, which runs on electricity, paired with a gas boiler for the provision of hot water and as a back up heating source. Carole and Kelvin had minimal knowledge about heat pumps before applying to the trial and they wanted to ensure that it would heat their house sufficiently to meet their needs. 

Prior to the installation, the couple had a full survey of their home to make sure that the right level of heating and hot water would be provided. Carole felt that the advice and suggestions of the surveyors and installers were critical to make them feel relaxed and reassured during the whole process. 

“Go ahead with it but be aware that it’s a whole new heating system installed, therefore it can’t be done without some disruption.”

For Carole and Kelvin, the two main benefits of their new hybrid heat pump are that their home is warmer and it has reduced their impact on the environment in the long term. The couple would definitely recommend heat pumps to other households. 

Installing the heat pump

How long did it take?

The system was installed in less than five working days by a team of accredited installers involving plumbers and electricians. The installation took longer than a typical heat pump installation, which usually takes 1–2 days, because they installed a hybrid heat pump, which involved connecting both a heat pump and a new gas boiler. 

What did it involve?

The couple were keen to move their heating system unit from the bathroom to the utility room, as they felt the latter was more spacious and convenient. The installers identified that this would indeed be the best solution. 

The outdoor unit was placed in the garden, below the kitchen window. The old radiators were replaced with new, individually controlled ones in every room, as they needed to be bigger for a low temperature heat pump. The pipework was also fully replaced. 

Were they happy with the result?

Carole had a great experience with her installers, commenting that she was well informed about the process. 

“I constantly felt that I knew what was going to happen.”

Common concerns about heat pumps

Disruption in the home

According to Carole, the level of disruption required during the installation will vary. It can be a ‘touch up’ job or more substantial work. In their case, apart from the old gas boiler, they also had to replace the pipework and all the radiators in the house. Therefore, there was a significant level of disruption and they needed to do some redecoration after the installation. However, they were both prepared that they would have to replace their old gas boiler at some point and now they are very happy with the results. 

Warmth and comfort

Carole and Kelvin used to have cold spots in their house. During the first few months after its installation, the heat pump showed that it can meet all of the couple’s heating requirements, even on the coldest days. This was due to the installers’ careful examination of each individual room during the pre-installation process to make sure that every room would be heated to the desired temperature. 

According to Carole, there is now a big difference in how warm the home feels compared to before. 

Aesthetics and ‘look’ of the heating unit

The couple were prepared for an outdoor unit to be placed in their back garden. Having travelled abroad and seen the large outdoor units that hotels use for air conditioning, they were happy that their unit was not as big. 

An important point that Carole highlights is that the outdoor unit will be more visible in a small garden rather than in a larger one. 


Carole and Kelvin have not found the heat pump to be noisy, even with the outdoor unit being placed just below their kitchen window. 

This case study is part of a series produced as part of a UK Government funded project through its Energy Innovation Programme, the Electrification of Heat Demonstration Project. The project is trialling different types of heat pumps in up to 750 homes across the UK.

Last updated: 20 April 2022