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The UK is a country with an extensive gas network, piped into homes for the last 50 years, ever since a major shift away from coal-fired heating in the 1960s.

As a result, it’s estimated that eight out of 10 UK homes is heated by a gas boiler. But if the country wants to reach its target of net zero carbon emissions then domestic heat pumps will need to be installed in at least half, but closer to 80% of homes by 2050, according to the parliamentary .

To that end, the previous Conservative administration under former Prime Minister Rishi Sunak set a target of installing 600,000 heat pumps a year by 2028, with a cumulative investment of £28 billion.

That spells a potentially huge opportunity for the construction sector but the UK only managed 59,862 installations in 2022. It was a 40% increase on the previous year but illustrates just how much ground needs to made up. It was also far fewer than the 462,672 heat pumps installed in France, 236,000 in Germany and 123,208 installed in the Netherlands during the same year, according to the UK’s .

Heatpump retrofits also involve the installation of insulation measures. (Image: Paul David Drabble/RPS Group)

In that sense, Together Housing, a social landlord responsible for managing nearly 39,000 homes in the north of England, is something of a trailblazer. It has committed to remove gas boilers from the 31,000 homes that currently contain them by 2035.

To achieve that, it is undertaking what it claims is the UK’s largest low-carbon retrofit project, installing heat pumps in around 750 properties a year at an annual cost of £10-11 million, starting with those containing the oldest boilers first.

The project began in 2022, with contractor Rothwells Plumbing Services (RPS) responsible for retrofits across Yorkshire as part of a four-year contract (a different contractor operates across Lancashire).

The vast majority of retrofit work involves heat pumps – air source heat pumps for houses and ground source heat pumps for medium-rise blocks of flats.

“But as well as installing the heat pump, we also install insulation measures to the fabric of the property,” says Jon Schofield, retrofit project lead at Together Housing. “That might be cavity wall insulation, loft insulation, under-floor insulation if it’s got a suspended floor.”

Infrastructure challenges

RPS and Together Housing have found that delivering a heat pump retrofit project at scale involves two principal challenges – the first a practical issue and the second more to do with communication with residents.

An installer works on retrofitting a heat pump to a residential property (Image: Paul David Drabble/RPS Group)

The practical issue has to do with the companies licensed to deliver electricity in the UK, known as distribution network operators (DNO).

Because heat pumps place a higher level of demand on the local electrical infrastructure, the DNO has to ensure that the cabling running to the homes being upgraded to is up to the task. And that’s something that is outside of the control of either the housing association or contractor.

“We have to get approval from the DNO before we can install a heat pump,” says Schofield. “We are doing these upgrades on a planned basis and at scale and typically the DNOs aren’t geared up to respond quickly enough to our requests – that slows us down a bit.”

“We’ve got the budgets in place internally within our business plans to deliver the volume of work which we want to do. We try and engage early with the DNO as much as we can,” says Schofield.

Meanwhile, Together Housing has put together a briefing for politicians on the bottleneck created by DNOs. It hopes that parliament groups and members will set out a new objective for the UK’s energy regulator Ofgem to guide a national approach to delivering net-zero retrofit projects, and an agreement between DNOs and social landlords to speed up connection work and avoid delays.

Early engagement

The second major challenge is to do with engagement of residents, potentially sceptical that heat pumps are an adequate replacement for their gas boilers. Together Housing has developed an engagement programme for residents called that vaunts the environmental benefits of switching heat pumps.

But as Graham Rothwell, owner and founder of RPS Group explains, the contractor also has a role to play.

Early engagement with residents has long been a part of social housing work, whether it is boiler replacement programmes or kitchen and bathroom installations, he explains.

“Engagement with residents is absolutely key – communicating the full, honest story about what is going to happen, how long it is going to take and the pros and cons,” Rothwell says.

“Now [with heat pumps] there are more technical attributes to take on board. And it’s more intrusive into the home than it ever has been. So that message has got to be clearer than ever.”

Residents need to understand that air source heat pumps are a completely different concept, designed to stay on permanently at lower running temperatures to save money and carbon, says Rothwell. “Once you have success with certain individuals in streets and communities, then word spreads and the engagement becomes easier,” says Rothwell.

Getting the design right

A plumber installs lagging to copper pipes on a residential property as part of a heatpump retrofit (Image: Paul David Drabble/RPS Group)

After that comes getting the supply chain right – selecting the right manufacturer to provide the backup and technical ability.

“One of the big lessons is designing the system properly. There’s been a lot of bad press around heat pumps over the years. Generally it’s not the heat pumps themselves, it’s bad installation and bad design. So making sure the designs are correct and it gets installed properly is critical,” says Rothwell.

Interestingly, however, given well-publicised concerns that there aren’t enough skilled people to handle the volume of heat pump retrofits envisaged for the next few years, this is an area that Rothwell appears more relaxed about.

“We’ve learned very quickly a successful model to be able to install these on time to budget and with satisfaction.

“A lot of the skillset is in place because it is a generic type of work that we do for putting radiators in - lifting floorboards, putting pipes in, putting wires in. It’s not much different. The commissioning process is where a new skillset comes in. So we have to upskill our staff to a certain level to fit part of the system, but we don’t have to upskill everybody to a technical level.

“Over time, we are training up more commissioning engineers so we can expand,” he says.

Retrofitting on a grander scale

What needs to happen before the we start to see heat pump retrofitting of existing housing stock happening at a grander scale?

Schofield addresses that question by explaining how it has worked for Together Housing. “We have commitments to this programme from board level downwards, from the chief executive down to myself who’s responsible for delivery it. We have a decarbonisation strategy with clear goals in place, clear timescales, and fully funded within the business plan,” he says.

“Others may find it more difficult because they don’t have those things in place. And again, there are also things outside of our control, like the issues with DNOs for example.”

Rothwell wants to see more positive messages from both central and local government. “There have been so many negative documentaries on television [about heat pumps] and it’s killing it. We have targets to hit and more clear, positive messages would give people the confidence to speak to the likes of Together Housing and learn their lessons and have a go themselves.”

He also wants to see more funding for training in the long term as well as better education around renewable energy in schools.

“And going back with the DNO, a bit of support and understanding from them would help because when we the infrastructure isn’t correct for us to install a system, it takes time to correct it,” he adds.

“There are so many positive messages heat pumps and retrofit is low-hanging fruit because you can make a big impact on people’s lifestyles, the economy and reducing CO2. So I think the approach that Together Housing has taken at a large scale is absolutely commendable,” he concludes.