Sub-standard and poorly installed insulation on heat pump systems is costing UK households around £74 a year in avoidable heat loss, according to government figures, as concerns grow over installation quality in the drive to decarbonise home heating.
The Department for Energy Security and Net Zero (Department for Energy Security and Net Zero) has acknowledged the issue, estimating that affected heat pump households are collectively losing around £20 million annually in wasted energy due to poorly insulated external pipework.
The admission was made at the Chartered Institution of Building Services Engineers (CIBSE) Decarbonisation Conference in London, where industry leaders and policymakers gathered to discuss progress in the UK’s heat transition.
The issue centres on external pipe insulation, which, if improperly fitted or of substandard quality, can lead to significant heat loss between the heat pump unit and the home. This reduces system efficiency and increases running costs, undermining some of the expected savings from electrified heating.
In response, energy services firm WattsWatt has launched a free support tool allowing households to check whether their external pipework has been correctly insulated. The service also enables users to estimate annual heat loss based on the length of exposed pipework.
WattsWatt analysts warn that the financial impact could grow substantially as deployment of heat pumps accelerates. Based on the government’s target of installing 400,000 units per year by 2030, the company estimates total annual losses from insulation issues could reach £82m if the problem is not addressed.
The findings add to wider concerns about the practical challenges of scaling up heat pump adoption across the UK housing stock, much of which was not designed with low-carbon heating systems in mind.
While heat pumps are a central pillar of the UK’s net zero strategy, critics have repeatedly highlighted issues with installation quality, upfront costs, and performance variability depending on property type and insulation standards.
Industry observers say the latest data underscores the importance of ensuring installation standards keep pace with rollout targets, warning that efficiency losses — even when relatively small per household — can quickly add up to high national costs.
The government has set an ambitious trajectory for heat pump deployment in the coming years as part of its broader decarbonisation agenda, but the emerging evidence suggests that delivery quality may prove just as important as installation volume in determining overall success.
For households, the issue is more immediate: even modest installation inefficiencies can translate into higher energy bills, reducing the expected financial benefits of switching away from gas heating.
Lisa Malyon, Co-founder and CEO of WattsWatt, said: “It’s quite straight-forward – if your external pipes aren’t insulated properly, the water cools as it travels through these outdoor pipes, affecting the temperature inside the house. To get the house back up to temperature, the heat pump has to work harder, which uses more energy.
“We first became aware of the issue when households complained their heat pump had stopped working – saying it was nowhere near as good as it had been when it was first installed. It turns out, their external pipework had been insulated with basic grey insulation designed for inside – and it was soaked through.”
Professor Richard Fitton, Professor of Building Performance at the University of Salford, comments WattsWatt’s heat pump check tool: “Heat pump technologies need careful design and installation for optimum performance. We are experimenting in the Energy House Labs to understand the heat losses associated with inferior external pipe insulation and will update on that soon.”
Chris Ridge of the Thermal Insulation Contractors Association (TICA) said: “Our latest white paper has established thermal insulation of pipework as a low-hanging fruit for decarbonisation. In the battle to win public trust for heat pump technologies we simply cannot afford the additional energy losses caused by incorrectly specified and installed thermal insulation on external pipe runs.
“The new WattsWatt campaign is helping to highlight a key issue that has otherwise remained under the radar for too long.”
Malyon added: “This avoidable issue risks undermining confidence in heat pumps unnecessarily. When households experience higher bills or lower comfort, the heat pump itself is often blamed, but in many cases it is not the technology – it is the installation detail.
“There’s a critical information gap for installers. The Microgeneration Certification Scheme’s MIS 3005-I installation standard doesn’t specify what type of insulation should be used outdoors. Instead, MCS refers installers to the heap pump manufacturers’ instructions, however these do not tend to specify what insulation is required either.”
Leave a Comment