The transition to renewable heating in Britain is supposed to be a story of progress: lower carbon emissions, cheaper bills, warmer homes. Yet behind the marketing lies a far more troubling reality. Poor design, corner-cutting and inadequate accountability continue to undermine confidence in heat pumps. Nowhere is this more evident than in the widespread use (and misuse) of buffer tanks in systems.
Buffer tanks are routinely presented as a benign addition to heat pump systems. Installers justify them as a way of increasing system volume, smoothing flow or protecting against operational issues. In theory, they can serve those functions. In practice, they have become a crutch for poor design, employed as a catch-all solution by installers who lack the skill, or the will, to engineer properly balanced systems. The consequences are calamitous: homes left cold, energy efficiency crippled and homeowners facing bills that make a mockery of the promises used to sell them renewable technology in the first place.
One case recently brought to light on the Renewable Heating Hub forums illustrates the depth of the problem. A homeowner, investing more than £22,000 in a new air source heat pump system, found themselves living with a house that could barely reach habitable temperatures. The system, installed less than two years ago, was plagued by undersized radiators, circulation failures and, most damaging of all, a buffer tank that created a 10 °C temperature loss between the heat pump and the radiators.
This is not a marginal issue. In a low-temperature system designed to operate at 45-50 °C, losing 8-10 °C to hydraulic distortion is fatal. Even when the heat pump was generating water at close to 50 °C, the radiators were only receiving 40 °C, wholly inadequate to heat the property. Independent analysis conducted by the homeowner confirmed the problem: thermal imaging, flow measurements and professional reports all pointed to a design that could never deliver comfort. Yet the installer insisted the system was “working at 350 per cent efficiency”. The reality was very different: measured seasonal performance was closer to 220 per cent, leaving the homeowner with higher bills than a gas boiler would have produced.
The financial toll has been immense. Beyond the original £22,000 outlay, the homeowner has spent hundreds more on independent assessments and faces further costs running into thousands to put things right. More than money, however, it is the sense of betrayal that stings. Careful due diligence was done. The installer was accredited, listed on respected networks and presented themselves as a trusted professional. Yet when the system failed, accountability evaporated. The installer dismissed the concerns, industry networks offered little practical help, and even attempts to pursue a Section 75 claim through a credit card provider were frustrated by the difficulty of obtaining remedial quotes in a market where most companies are reluctant to touch someone else’s failed installation.
This story should alarm everyone who cares about the future of heat pumps in Britain. Because while it is particularly stark, it is far from unique. Buffer tanks are still being dropped into systems across the country with little thought for how they will affect hydraulics. The result is a pattern of distorted flows, short-circuiting pumps and crippling efficiency losses. Low-temperature heating systems are not forgiving. They demand precision: correctly sized emitters, properly calculated pipework and carefully balanced circuits. Insert a poorly set-up buffer into that equation, and the design collapses.
What is most troubling is that much of the industry appears to accept this as normal. Buffers are still fitted as a default, almost an insurance policy, and the losses they introduce are brushed aside as inevitable quirks of renewable heating. They are not. They are the by-product of design laziness. The idea that this level of mediocrity is acceptable, that homeowners should spend tens of thousands only to end up colder and poorer, is indefensible.
Consumers must be far more demanding. The lesson from this case is simple: do not accept buffer tanks in domestic heat pump systems unless their necessity is proven beyond doubt. If an installer cannot design a system to function properly without one, they are not competent to be installing heat pumps. Buffers should be the exception, not the rule. And when they are used, they must be correctly balanced and commissioned by someone who understands exactly what they are doing. At present, that level of expertise is sorely lacking.
There is also a systemic failure of accountability. Accreditation bodies and industry networks cannot continue to wash their hands of responsibility once a badge has been issued. If an installer mis-sizes radiators, misplaces pumps and installs a buffer that robs a system of its efficiency, the accrediting body should intervene, not retreat behind disclaimers. Otherwise, the credibility of these schemes, and by extension the entire heat pump agenda, will collapse.
For government, regulators and consumer bodies, the implications are clear. The success of heat pumps depends not on subsidies or targets alone, but on the confidence of ordinary homeowners. Every time a poorly designed system leaves a family shivering in their own home, it is not just that household’s faith that is eroded, but the public’s faith in the entire transition to low-carbon heating. Cases like this do not just damage one brand or one installer. They damage the cause of decarbonisation itself.
Britain cannot afford that reputational harm. We cannot afford another generation of “renewable heating horror stories” circulating in forums, social media feeds and newspaper columns. If installers do not step up, if training bodies do not raise the bar and if accountability structures do not deliver real protection for consumers, then the market will fail.
The buffer tank debate may sound technical, but at heart it is about something simple: competence. Heat pumps are unforgiving of sloppy design. They require precision, care and accountability. When those are absent, as this case so painfully demonstrates, the outcome is failure… costly, uncomfortable, avoidable failure. And if the industry does not root out that failure, it risks undermining the very technology it claims to champion.