From cold-climate performance to suitability for older buildings, heat pumps remain widely misunderstood. In reality, they are mechanically simple systems based on established principles of physics, with performance outcomes driven by design decisions rather than inherent limitations
Heat pumps work. With essentially one moving part, their beauty lies in their simplicity. Rather than generating heat, they transfer it — a process governed by well-understood physical laws. This simplicity underpins their reliability, longevity, and efficiency, and explains why the core principle has remained unchanged for more than a century.
One kilowatt of electricity, combined with between two and five kilowatts of naturally occurring low-grade heat, can deliver up to 6kW of useful heat, resulting in efficiencies in the range of 300 to 600%.
This is because a heat pump does not make heat in the traditional sense. It uses a small amount of electricity to collect and move heat that already exists in the surrounding air, ground, or water. Most of the warmth delivered to a building is therefore drawn from the environment, not generated by the system itself.
Decades of abundant, low-cost gas have entrenched a narrow way of thinking within the industry.
The default response has been to install a gas boiler for heating and a separate heat pump, used as a chiller, for cooling, even though a single, well-designed heat pump system can provide both.
The performance of a heat pump is largely determined by two factors: the temperature it draws heat from, its source and the temperature it needs to deliver, its load side.
The closer these temperatures are to one another, the less effort the system has to expend. In practical terms, this means the compressor works less, energy use falls, and overall efficiency increases.
Heat pump systems are generally categorised by the source from which they extract low-grade thermal energy: air, ground, or water.
Air source heat pumps exchange heat with the ambient air, extracting thermal energy for heating or rejecting heat to the atmosphere when operating in cooling mode. Ground source heat pumps extract low-grade thermal energy from the earth via either vertical boreholes drilled to depth or horizontal collector arrays installed, typically around one metre below ground level.
Water source heat pumps draw thermal energy from bodies of water such as lakes, rivers, underground aquifers, or from engineered processes where water is used as the primary heat transfer medium.
Heat pumps: Myth-busting Q&A
Myth: Do heat pumps work in cold climates?
Fact: Yes. A cold climate doesn’t matter to a ground source heat pump, as the ground stays at a constant temperature. Air source heat pumps are designed to extract heat even when outdoor temperatures are low. A typical refrigerant in an air source heat pump boils at –20 °C, which is how air source heat pumps work. While efficiency naturally falls as temperatures drop, modern systems are engineered to operate reliably in cold conditions and are widely used in northern Europe, Scandinavia, and Canada.
Myth: Heat pumps cannot heat older or poorly insulated buildings.
Fact: They can, but the approach matters. Older buildings often have higher heat losses and were designed around high-temperature heating systems. Changing from a high temperature intermittent heating on a timer to variable temperature, consistent flow works very well in National Trust style properties and older homes where conservation or preservation is as important as comfort heating.
Myth: Heat pumps are expensive to run.
Fact: Running costs depend on system design, electricity prices, and how well the building retains heat. When properly sized and installed, heat pumps can deliver three to five units of heat for every unit of electricity used, which can offset higher electricity costs compared with gas. The UK has the greatest difference between gas and electricity costs, for a typical domestic tariff, it is in excess of 4 times, which does not support the government’s aspirations to decarbonise heating by electrification. Fortunately, some utility providers are creating flexible tariffs to reward those with heat pumps, reducing running costs further.
Myth: Heat pumps only work with underfloor heating.
Fact: No. While underfloor heating is well-suited to heat pumps because it operates at lower temperatures, radiators, fan-coil units, and air systems can also be used. The key is matching the heat-delivery system to the operating temperature of the heat pump. There are examples of poorly installed underfloor heating systems requiring higher temperatures than radiators to achieve the required thermal output.
Myth: Heat pumps are complicated or unreliable.
Fact: In practice, heat pumps are mechanically simple, with few moving parts and no combustion. Reliability is typically determined by system design, installation quality, and controls rather than the technology itself.
Myth: Can one heat pump really provide both heating and cooling?
Fact: Yes. Heat pumps produce heat on one side and cool on the other. With the right design and controls, a single system can provide heating in winter and cooling in summer, and in some cases do both at the same time.
Myth: Heat pumps are noisy.
Fact: Domestic ground source heat pumps operate at noise levels equivalent to refrigerators and are designed to be installed in the same space as white goods, kitchens or utility rooms. Air source heat pumps have the addition of a fan designed to move large amounts of air. Those with larger evaporators (heat exchangers) have lazier fans and produce less noise. Proper installation and maintenance can further minimise noise levels.
Heat pumps work. Simply.
They are not defined by novelty or complexity, but by the consistent application of well-understood principles. When properly designed and matched to their task, heat pumps deliver heating and cooling efficiently, reliably, and at scale. In a landscape often shaped by habit and misconception, their continued relevance lies in doing exactly what they have always done — moving heat, quietly and effectively.
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