INDUSTRY COMMENT: NIBE


Designed to perform: why system design is the missing link in low-carbon heating


Performance starts long before installation


There is a tendency within the sector to focus on installation quality and commissioning, both of which are critical. However, by the time a system reaches site, many of the key decisions that will determine its performance have already been made.


System design defines how a heat pump interacts with the building, the distribution system and the end user. It influences flow temperatures, emitter sizing, hot water delivery and overall system balance. When these elements are aligned, systems operate efficiently and consistently. When they are not, even well-installed systems can struggle to perform.


While heat pumps are widely recognised as a key low carbon heating solution, supported by growing incentives, increased awareness, and expanding installer networks, the challenge remains that performance in real-world installations does not always match expectations. Systems that should deliver high efficiency and comfort can fall short, leading to higher running costs and reduced confidence among homeowners. Mike Dungworth, head of technical at NIBE Energy Systems Limited explains that in many cases the root cause is not the technology itself, but how the system has been designed and installed


This is particularly important in the context of low-temperature heating. Heat pumps operate most efficiently when designed as part of a system that supports lower flow temperatures. Without this, systems may rely on higher temperatures to compensate, reducing efficiency and increasing running costs.


The difference between specification and design


As demand for heat pumps increases, there is a risk that system design becomes simplified into a process of product specification. While selecting the right unit is important, it is only one part of a much broader equation.


Specifying a heat pump without fully considering the wider system can lead to suboptimal outcomes. Factors such as heat loss calculations, emitter sizing, hydraulic configuration and control strategy all play a role in determining how the system will perform over time. True system design requires a more holistic


approach. It means understanding how each component interacts, how the building behaves under different conditions and how occupants will use the system in practice. This distinction becomes increasingly important as the industry moves towards higher volumes of installation. At scale, small design compromises are repeated across thousands of homes, amplifying their impact.


Common design challenges in practice


Many of the performance issues observed in the field can be traced back to early-stage design decisions. These include:


• Systems sized without accurate or up-to- date heat loss calculations


• Emitters that are not specified for low- temperature operation


• Hydraulic layouts that affect flow, balance and heat transfer


• Where considerations for domestic hot water provisions fall short of requirements.


• Control strategies that do not reflect how the system will be used day-to-day


Individually, these issues may appear minor. Collectively, they can significantly affect efficiency, comfort and reliability. Addressing these challenges does not require fundamentally new technology, but it does require greater attention to detail and a more consistent approach to system design.


Designing for scale and consistency


The UK’s decarbonisation targets depend on the ability to deliver low-carbon heating at scale. This introduces a new level of complexity, where consistency becomes just as important as capability.


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At small volumes, experienced designers and installers can often compensate for design shortcomings. At scale, this becomes far more difficult. Systems must be designed in a way that can be replicated reliably across different property types, regions and installer teams. Standardisation has a role to play, but it must be applied carefully. Standard approaches should provide a framework for consistency while still allowing for the specific characteristics of individual buildings. Getting this balance right is essential to achieving both scale and performance.


The role of industry collaboration


Improving system design is not the responsibility of any single part of the supply chain. It requires collaboration between consultants, installers, manufacturers, and training providers. Consultants and specifiers play a critical role in setting the direction of projects, particularly in larger developments. Installers bring practical insight into how systems perform on site. Manufacturers can support both groups by providing design guidance, technical resources and integrated solutions that simplify complexity without compromising performance. Training also has a key role to play. As systems become more sophisticated, the ability to design, interpret and implement effective solutions becomes an increasingly important skill, including product and accessory understanding.


Building confidence through better design


Ultimately, the success of low-carbon heating will be judged not by the number of systems installed, but by how well they perform over time. Well-designed systems deliver stable comfort,


predictable running costs, and reliable operation. They require less intervention, generate fewer callbacks, and build confidence among homeowners. Poorly designed systems, by contrast, can undermine trust in both the technology and the wider transition. As the industry moves forward, there is an opportunity to place system design more firmly at the centre of the conversation. By doing so, the sector can move beyond simply deploying low-carbon technologies towards delivering outcomes that meet expectations in real homes. Performance does not begin at commissioning; it begins at design.


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