Why Heat Pumps Often Get Blamed for Problems They Didn't Cause
A heat pump gets installed. The building runs a little cold, the running costs surprise everyone, and within a few months the technology itself gets the blame.
Often, that's the wrong verdict. Most of the disappointing heat pump installations we come across trace back to how the system was designed, controlled or commissioned - not to the heat pump itself.
Heat pumps versus boilers - a genuinely different starting point
A boiler generates heat by burning fuel and can comfortably deliver high flow temperatures on demand. A heat pump extracts heat from the air, ground or water outside and moves it indoors - and it does that most efficiently at lower flow temperatures than a boiler was ever designed around. Installing a heat pump into a system designed and sized for a boiler, without revisiting that design, is where a lot of the disappointment starts.
Flow temperature is the number that actually matters
A heat pump's efficiency - its Coefficient of Performance, or COP - falls as the flow temperature it's asked to produce rises. Run one at a boiler-era flow temperature to compensate for undersized radiators or poor distribution, and its efficiency advantage over a boiler shrinks, sometimes substantially. Run it at the lower flow temperature it's actually designed for, with distribution sized to suit, and the efficiency case looks very different.
Insulation myths, cut both ways
It's true that a poorly insulated building makes any heating system work harder. It's not true that a building needs to be insulated to some perfect standard before a heat pump can work at all - that's an oversimplification that's put people off perfectly viable projects. What actually matters is whether the heat pump and the distribution system have been sized to match the building's real heat loss, insulated as it actually is, not sized against a generic assumption.
Controls and commissioning - where a lot of underperformance actually lives
A heat pump that's been commissioned properly, with its controls genuinely tuned to the building's real heat loss curve rather than left on a generic factory setting, behaves very differently to one that hasn't. Weather compensation, correctly set flow temperatures, and properly balanced distribution do more for real-world performance than most people expect - and their absence is one of the most common, least visible causes of a heat pump earning a bad reputation.
Electricity tariffs change the economics, not the physics
A heat pump's running cost depends on the electricity tariff it's running against, not just its efficiency. The same heat pump can look excellent or mediocre purely because of when it's actually drawing power and what that electricity costs at the time - which is a tariff and control question, separate entirely from whether the heat pump itself is a good one.
Thermal storage as the quiet enabler
Storing heat rather than storing electricity - a buffer or thermal store - can let a heat pump run at efficient, steady output rather than cycling to match instantaneous demand, and can shift more of its running time towards cheaper electricity periods. It's a genuinely useful lever that gets far less attention than the heat pump itself.
When a heat pump genuinely isn't the right answer
None of this means every building suits a heat pump today. Some genuinely need fabric improvements or distribution upgrades first to make the economics and comfort work properly, and some processes need temperatures a heat pump can't sensibly deliver. The point isn't that heat pumps are always right - it's that the verdict on whether one was a good decision shouldn't be reached without first checking whether it was actually designed, controlled and commissioned properly in the first place.
Sources and further reading
A disappointing heat pump is often a design or commissioning problem, not a technology problem - and the two get confused more often than they should. If you're weighing up a heat pump project, or trying to work out why an existing one isn't performing, get in touch.