7 Signs Your Heat Pump May Not Be Installed Correctly

7 Signs Your Heat Pump May Not Be Working Correctly

One of the biggest problems homeowners face after a heat pump installation is simply not knowing what normal looks like. Unlike a gas or oil boiler, a heat pump behaves very differently and because most people have no reference point for how these systems should sound, feel, or perform, genuine problems can go unaddressed for months. Whilst many systems perform brilliantly from day one, we regularly speak to UK homeowners experiencing ongoing issues caused by incorrect setup, poor commissioning, or design errors that were never properly identified at installation.

Homeowners are often reassured with phrases like "heat pumps are supposed to run constantly," "radiators should feel cooler than with a boiler," or "the system just needs time to settle." And whilst those statements can sometimes be true, they can also be used to mask real installation and configuration problems that are costing money and causing discomfort. If something feels wrong with your system, it is usually worth investigating properly rather than simply accepting a dismissive explanation. Here are the seven most important warning signs we see when a heat pump system may not be operating as it should.

Sign 1: The House Never Feels Properly Warm

If your heat pump runs for long periods but parts of the house remain cold or uncomfortable, that is one of the clearest signs that something is not right. Heat pumps are designed to maintain a steady background warmth throughout the property not just some rooms while others stay cold. When this pattern occurs, the most common underlying causes are undersized radiators that cannot deliver enough heat at lower flow temperatures, incorrect flow temperature settings that are too low for the property's heat demand, poor system balancing that starves certain radiators of adequate flow, zoning problems that prevent certain areas from receiving heat when they need it, or inaccurate heat loss calculations that meant the system was designed around wrong assumptions from the start. Our full guide on why some rooms are cold with a heat pump covers each of these causes in detail. A real-world example can be found in our case study on a house that never reached temperature due to incorrect heat loss and undersized radiators, where the installer was ultimately required to return and upgrade the system at no cost.

Sign 2: Electricity Bills Are Extremely High

It is true that electricity usage increases after switching from gas or oil to a heat pump, because the heat pump now handles all of the heating demand that was previously split across multiple fuel sources. However, there is a significant difference between a predictable increase in electricity usage and bills that are genuinely disproportionate. Unusually high running costs after a heat pump installation are often caused by flow temperatures that have been set far too high sometimes at 60°C or above which forces the heat pump to work far harder than it needs to. Immersion heater usage that has never been scheduled correctly is another frequent culprit, quietly adding substantial electricity costs completely independently of the heat pump itself. Poor control setup, cycling problems, and inefficient commissioning settings all contribute to unnecessary electricity spend. Our article on why heat pumps are so expensive to run explains the difference between normal running costs and a genuine efficiency problem, and our guide on how to reduce heat pump electricity bills offers practical steps. We have also documented a detailed case study on why one homeowner's electricity bills doubled after a heat pump install, where flow temperature correction made a dramatic difference.

Sign 3: The Heat Pump Keeps Turning On and Off

Frequent starting and stopping known as short cycling is a clear signal that something is wrong. A well-configured heat pump should run in long, steady cycles, particularly during colder weather. Short cycling is almost always caused by an identifiable problem: the system may be oversized for the property's heat demand, the water volume in the system may be too low to provide a stable load, the controls may be incorrectly configured, or there may be a hydraulic issue preventing adequate flow. Over time, short cycling reduces system efficiency significantly and places additional mechanical strain on the compressor and other components. Our article on why a heat pump keeps turning on and off covers the full range of causes in detail. A relevant case study is our Essex new-build where a COP of just 1.2 was traced to nine underfloor heating zones causing constant cycling a fixable problem that had been left in place since installation.

Sign 4: Some Rooms Never Heat Properly

If particular rooms consistently fail to warm up while the rest of the house is comfortable, the issue is almost always specific to either the radiator sizing in those rooms, the system balancing, or the circulation reaching those circuits. Extensions, loft conversions, and larger rooms with high glazing are especially prone to this problem because they were often added or modified after the original heating system was designed, and their heat demand was never properly reassessed. Older properties with solid walls or north-facing rooms with significant heat loss are also commonly affected. Our guide on do heat pumps need bigger radiators explains why radiators that worked acceptably with a boiler can genuinely underperform at heat pump flow temperatures, and our article on heat pump system balancing explained covers how uneven flow distribution causes cold spots across the property. The case study on a Victorian terrace in Bristol with lukewarm radiators on cold days is a good example of how a well-functioning heat pump can still produce cold rooms when the surrounding system has an underlying fault.

Sign 5: The Controls Were Never Properly Explained

This happens far more often than most homeowners realise, and it causes significant ongoing problems that could have been avoided with a proper handover. Many homeowners are left with unfamiliar thermostats, weather compensation curves, hot water schedules, and installer menu settings that were never explained to them at the time of installation. As a result, systems are frequently left running in inefficient default settings for months sometimes years with no one realising that a straightforward configuration change could dramatically improve both comfort and running costs. Weather compensation in particular is one of the most powerful tools available for keeping a heat pump running efficiently, but it is one of the most commonly left either disabled or incorrectly configured. Our guide on how to set weather compensation on a heat pump and our article on what weather compensation actually does are both worth reading if you are unsure how your system is currently configured. Our case study on a heat pump that seemed to have a mind of its own due to conflicting thermostat controls shows how quickly a controls problem can be resolved once it is properly identified.

Sign 6: The Heat Pump Defrosts Constantly

Some defrosting during cold or damp weather is completely normal behaviour for an air source heat pump. When outdoor temperatures are low and humidity is high, ice can form on the outdoor coil and the system needs to run a defrost cycle to clear it. However, excessive or unusually frequent defrosting is a warning sign worth taking seriously. It can indicate poor flow rates that prevent the heat pump from operating efficiently, blocked filters or dirty coils reducing heat exchange, insufficient water volume in the system, heat loss in external or underground pipework that is destabilising system temperatures, or circulation problems preventing adequate flow through the heat exchanger. Our article on why a heat pump defrosts so often explains the difference between normal and excessive defrost behaviour clearly. The case study on a heat pump freezing up repeatedly due to pipework and system design issues shows how underlying design faults caused far more aggressive icing than should ever occur, and how redesigning the pipework layout resolved the problem completely.

Sign 7: The Installer Never Performed Proper Commissioning

Proper commissioning is one of the most important steps in any heat pump installation and one of the most frequently skipped or done inadequately. A fully commissioned heat pump system should include flow rate checks and balancing adjustments, control setup and weather compensation configuration, system testing across different operating conditions, and a clear homeowner handover explaining how the controls work day-to-day. Unfortunately, some systems are installed mechanically correctly but never fully optimised afterwards. The heat pump gets switched on, the house heats to some degree, and the installer signs off and leaves. The result is a system that technically works but is running inefficiently, with settings that are not suited to the specific property. Our article on common commissioning mistakes with air source heat pumps covers the most frequent failures we see in detail, and our guide on how to know if your heat pump was installed correctly gives homeowners a clear framework for assessing their own installation.

What a Good Heat Pump Installation Should Feel Like

A properly installed and commissioned heat pump system should provide steady and comfortable temperatures throughout the property, reasonable running costs relative to the size and insulation level of the building, stable and quiet operation without frequent cycling or error codes, consistent and reliable hot water, and a level of confidence from the homeowner about how to operate the system correctly day-to-day. Not every issue means the heat pump has been installed badly. Sometimes systems simply need adjustment, optimisation, or better homeowner understanding of how heat pumps work differently to boilers. But if something feels wrong, it is always worth investigating properly rather than being told that is simply how heat pumps work. Our Full Performance Review provides independent remote troubleshooting to identify exactly what is happening and what practical steps will improve performance, and our Pre-Installation Design and Heat Loss Review helps homeowners catch potential design and sizing issues before installation begins.