High temperature heat pumps could be the gamechanger we need for retrofit
Half of all homes will need a heat pump by 2040. That was the advice issued earlier this year by the Climate Change Committee when asked whether the UK was on course to reach Net Zero by 2050; and what we needed to do to ensure we meet our legal obligations.
And it’s no secret that heat pumps provide an excellent alternative to fossil fuels, as they create significantly less CO2 than boilers running on gas or oil.
Then there’s the data on fuel poverty. Low-income households with poorly insulated homes spend a higher percentage of their income on energy bills. You only need to look at the volatility in gas prices over the last few years to understand why the transition to more sustainable heating solutions, which will mitigate this volatility, is crucial to reducing household susceptibility to fuel poverty.
The choice between heating or eating is an increasing reality for some, so it’s vital that housing providers continue make their homes warmer, more affordable and comfortable for their customers.
We’ve been on this journey for some time, using our Homes and Place standard to guide our thinking, help us determine investment priorities, and bring more of our homes up to the standards of comfort we want for our customers, while mapping a pathway to Net Zero.
When you take these arguments together, the rationale for retrofitting homes with sustainable alternatives, such as heat pumps, is obvious even without the legal obligation.
But as we know – the need to install low carbon heating was never really in question.
Instead, the challenge has been the installation in existing homes, which was costly, time-consuming and disruptive as it was believed that especially old, microbore pipework had to be replaced. And not only that, but to install a low temperature heat pump, which is all that has existed on the market until recently, you had to replace most of the pipework. This has meant lifting or replacing carpets, removing radiators and carrying out plenty of redecoration work afterwards.
Understandably many of our customers have found this disruption off putting.
But there is good news. Our recent pilot with Mitsubishi Electric and their pioneering range of Ecodan R290 High Temperature Air Source Heat Pumps (HTASHP) has turned the assumption that heat pumps cannot be fitted with legacy microbore pipework firmly on its head.
The early findings from this trial, which saw us retrofit six of our homes with HTASHPs, shows that it is possible to retrofit homes and keep the existing radiators and pipework. It’s an exciting development, and a potential game changer for the sector.
By significantly reducing the level of disruption to the customer and allowing existing pipework, radiators and floor coverings to remain, it mitigates a significant time and cost barrier to large-scale heat pump retrofitting in our homes.
The findings to date also tell us that the installation of a high temperature heat pump can take as little as two days, which is around 40% quicker than it currently takes SNG to install a low temperature heat pump, pipework and radiators.
And then there’s the cost. Being able to keep the existing pipework and radiators, while reducing the need to redecorate means for every home we retrofit we could save up to £2000 per house. Across our gas heated portfolio, this could represent significant savings – which as a not-for-profit, means we can invest more in our customers’ homes and provide greater value for money.
SNG is investing £0.5bn over the next 10 years to enable us to retrofit 1,500 homes every year to reach a minimum of EPC B+. In addition to our own funding, we’re using £9.8m from the Social Housing Decarbonisation Fund (SHDF) Wave 2, over £19m from SHDF Wave 2.1 and £36.5m from the Warm Homes Fund to help us on our retrofit journey.
While the introduction of medium to high temperature ASHP’s will create a small drop in efficiency and therefore generate slightly higher running costs in comparison to low temperature air source heat pumps - no heating technology is completely without its limitations. It is, however, possible to mitigate some of this by ensuring the high temperature heat pumps can adjust to the weather conditions and do not operate at a fixed flow. In addition, we can also invest the money saved from lower installation costs into other measures that would generate and store electricity for the home, saving residents more on their bills.
The findings from this trial open the door for more providers to scale-up their Net Zero efforts in the knowledge that they don’t have to compromise on the comfort of their customers or incur unnecessary costs.
Early next year we will have additional data from more retrofit pilot projects we’re carrying out in 110 occupied homes. These are exploring differing heating, hot water and energy generation, distribution and storage systems - including HTASHPs.
For now, we’re excited by the potential of high temperature heat pumps. We’ll take the data from all our trials to understand the optimal technologies for retrofit, to inform our approach to making our customers’ homes more efficient and comfortable.
First published in Inside Housing on 1 August 2025