07/03/2026
Most Heat Pump Complaints Start With the Heating System, Not the Heat Pump
Across the UK, Ireland and Germany, many complaints about heat pump installations follow the same pattern.
High running costs.
Poor comfort.
Unstable heating behaviour.
The appliance is usually blamed.
The cost of electricity is often blamed.
But in many cases, the real issue lies somewhere else.
Single-circulator heating systems that lack a properly designed hydraulic structure.
In these systems, multiple circuits share the same pump and the same return path. As the building load changes and flows shift throughout the system, the circuits influence one another.
The result is that return temperatures from different circuits blend before reaching the heat pump.
The appliance then reacts to an average signal, rather than the true condition of the building loads it is supposed to serve.
The simple illustration below shows the principle.
If one foot is in water at 43 °C and the other at 40 °C, the average temperature might be 41.5 °C.
But that number tells you very little about what either foot is actually experiencing.
Hydronic heating systems behave similarly when return temperatures from different circuits are blended.
When that happens, the heat pump controller is operating on distorted information, which can lead to unstable operation, higher running costs, and poor comfort.
Many of the complaints now emerging about heat pumps are not caused by inefficient appliances.
They are the result of system structures that prevent the appliance from observing the building's true behaviour.
Understanding the hydraulic structure of the system is therefore just as important as selecting the appliance itself.
