Air source heat pumps (ASHPs) have rapidly moved from a niche sustainability technology to a central consideration for domestic hot water (DHW) at commercial scale. As UK public sector organisations seek to reduce carbon emissions and strengthen ESG performance, increasingly stringent building regulations are positioning heat pumps as one of the most viable routes, particularly in new builds, to low-carbon hot water.
Unlike conventional boilers, ASHPs do not generate heat through combustion. They use electricity and a refrigerant circuit to extract thermal energy from ambient air and transfer it into a DHW system. Under favourable conditions, modern systems can achieve high coefficients of performance (COP), delivering three to four units of heat for every unit of electricity consumed. This efficiency provides significant carbon-saving potential compared with direct electric or gas heating alone.
Policy is also accelerating adoption. Building decarbonisation across the public sector remains central to the UK’s net-zero strategy, with electrification of heat expected to play an increasingly important role. As a result, low-carbon heating is moving from an optional sustainability measure towards an important consideration for future building compliance.
However, commercial DHW presents challenges often overlooked in general discussions about heat pumps. Hotels, student accommodation, care homes, healthcare facilities, leisure centres and educational establishments can require large volumes of hot water during concentrated peak periods. They must also manage legionella risk, typically requiring stored water temperatures of at least 60°C. Heat pumps achieve their highest efficiencies at lower temperatures.
This creates a key challenge. An ASHP can efficiently raise incoming water temperatures to around 55°C, but consistently achieving higher temperatures can reduce efficiency and increase electricity consumption. Higher-temperature ASHPs can also be more expensive, larger and heavier, adding installation complexity.
Refrigerant choice further complicates specification. The European Union’s F-Gas Regulation 2024/573 has accelerated the move towards lower-GWP alternatives to traditional HFC refrigerants. Natural refrigerants such as carbon dioxide (CO₂) and propane (R290), capable of supporting higher-temperature production, are consequently attracting attention.
Refrigerant selection, however, cannot be based solely on environmental or heat-generating credentials. CO₂ systems can present operational challenges in some DHW applications, while propane’s high flammability requires careful consideration of system design, installation and maintenance. At Adveco, we have chosen not to carry large propane ASHPs, favouring more compact, lightweight and cost-effective R32 systems through our ADV-W range. We believe propane units are currently better suited to smaller-scale applications while safety considerations continue to be addressed.
Successful commercial DHW design is therefore less about maximising heat pump output and more about intelligent system integration. Hybrid systems offer a pragmatic response. Heat pumps can provide most annual energy input while operating within their most efficient range, with a secondary heat source, preferably an electric boiler, providing temperature uplift and supporting peak demand.
Appropriately sized thermal storage is equally important. Traditional gas-fired systems often combined high heat input with relatively small storage volumes. Heat pump systems benefit from reversing this principle. Larger cylinders allow water to be heated gradually, enabling the heat pump to operate steadily and efficiently while maintaining sufficient reserves for periods of peak demand.
For building owners and estates managers, the priority should therefore be demand rather than technology. Robust metering, consumption analysis and accurate assessment of peak loads should precede equipment selection. A well-designed hybrid solution, such as Adveco’s award-winning FUSION, can offer better efficiency and lifecycle value than simply specifying a larger standalone heat pump.
Ultimately, ASHPs are a proven option for well-designed commercial DHW applications, but they are neither a universal boiler replacement nor a silver bullet for decarbonisation. Their greatest value comes from combining heat pumps, appropriate storage and intelligent system integration. A pragmatic, demand-led approach can reduce emissions and operating costs while delivering resilient hot water systems fit for a low-carbon future.
