Why Commercial Heat Pumps Underperform After Installation
Why Commercial Heat Pumps Underperform After Installation — and How to Prove It with Data
Commercial heat pumps are now central to many public sector and commercial decarbonisation projects. They are regularly used to replace or reduce gas boiler consumption in schools, leisure centres, offices, healthcare buildings and local authority estates.
On paper, the case is often strong: lower carbon emissions, improved EPC/DEC performance, reduced reliance on fossil fuels and access to funding routes such as the Public Sector Decarbonisation Scheme.
But in practice, many heat pump systems do not perform as well as expected after installation.
The issue is rarely that “heat pumps don’t work”. More often, the problem is that the system around the heat pump has not been designed, commissioned, controlled or monitored properly.
The performance gap
A heat pump’s efficiency is usually expressed as COP — coefficient of performance. A COP of 3.0 means the system produces 3 kWh of heat for every 1 kWh of electricity consumed.
However, the actual COP achieved on site depends heavily on:
Flow temperature
Return temperature
System volume
Hydraulic design
Weather conditions
Control strategy
Domestic hot water temperatures
Defrost cycles
Buffer vessel arrangement
Heat emitter sizing
Commissioning settings
Whether boilers are still operating unnecessarily
A design-stage seasonal COP may look acceptable, but the real system may operate at a much lower efficiency if the return temperature is too high, the heat pump cycles repeatedly, or the system is constantly forced to operate at high flow temperatures.
Common causes of poor heat pump performance
One of the most common issues is excessive flow temperature. The higher the heat pump flow temperature, the lower the efficiency. This is especially important on retrofit projects where existing radiators, coils, calorifiers or plate heat exchangers may have originally been selected for gas boiler temperatures.
Another common issue is poor heat transfer. For example, a domestic hot water cylinder coil may be too small for the heat pump duty, causing the return temperature to rise quickly. The heat pump then cycles on and off rather than running steadily. This can reduce efficiency, increase running cost and shorten plant life.
Hydraulic problems are also common. If buffer vessels, pumps, low loss headers or plate heat exchangers are not arranged correctly, the heat pump may not see the flow rate or temperature differential it needs.
Control strategy is another major factor. If boilers are enabled too early, or if the BMS is not configured correctly, the system may rely on gas when the heat pump could have met the load.
Why monitoring matters
Without live performance data, it is very difficult to know what is actually happening.
A site may have a low-carbon heating system installed, but the client may not know:
How much heat the heat pump is producing
How much electricity it is consuming
What COP it is achieving
Whether it is cycling
Whether the boilers are operating unnecessarily
Whether the system is meeting the original design intent
Whether the client is saving carbon and cost as expected
This can lead to disputes between the client, designer, installer, manufacturer and controls specialist. Each party may have a different opinion, but without data, it is difficult to prove the root cause.
What should be monitored?
For a commercial heat pump installation, useful monitoring points typically include:
Heat pump electrical energy consumption
Heat pump thermal energy output
Flow and return temperatures
Outside air temperature
System flow rates
Heat pump status
Fault signals
Boiler enable/status
Buffer vessel temperatures
Domestic hot water temperatures
BMS setpoints
Pump status
Daily and monthly COP
COP against outside air temperature
The most useful insight often comes from combining the data. For example, COP plotted against outside air temperature can show whether the heat pump is broadly performing as expected, while flow and return temperature trends can reveal whether the system is operating at unnecessarily high temperatures.
The value to clients
For end clients, monitoring is not just a technical exercise. It helps answer commercial questions:
Am I getting the carbon savings I was promised?
Is the heat pump cheaper or more expensive to run than expected?
Is the system operating correctly?
Are there defects or commissioning issues?
Do I have evidence for future funding applications?
Can I improve future heat decarbonisation designs using real data?
For organisations with multiple buildings, such as councils, academy trusts, leisure operators or estates teams, this information becomes even more valuable. It allows future projects to be based on measured performance rather than assumptions.
Jupiter Engineering’s view
At Jupiter Engineering, we believe heat pump projects should not end at practical completion. A well-designed system should be monitored, reviewed and optimised so the client can confirm that the building is performing as expected.
Good design matters. Good commissioning matters. But without performance monitoring, clients are often left relying on assumptions.
Real data gives clients the evidence they need to understand whether their decarbonisation project is working — and what needs to be improved if it is not.
Need help reviewing or monitoring a commercial heat pump system? Jupiter Engineering can support design reviews, heat decarbonisation plans, troubleshooting and live performance monitoring.