The NHS is on a mission to become the world’s first Net Zero national health service. As one of the UK’s largest energy consumers, its vast estate — including hospitals, clinics, and healthcare facilities — accounts for around 15 per cent of total public sector emissions.1
Due to the need to maintain safe and comfortable environments for patients, staff, and sensitive medical equipment, heating and cooling account for the biggest energy demands in the NHS, and are among the biggest contributors to the NHS’s carbon footprint. Heating alone accounts for a significant proportion of the NHS’s 5% share of total UK emissions, making it a major area for intervention in the transition to Net Zero.2
Heat pumps’ emergence
Traditionally reliant on gas-fired boilers and steam heating systems, the NHS now faces a major challenge: transitioning to low-carbon heating solutions that can deliver the efficiency, reliability, and resilience, required for 24/7 healthcare operations. Heat pumps are emerging as a key technology in this transition. By extracting heat from the air, ground, or water, heat pumps can provide hospitals with efficient, low-carbon heating and cooling while significantly reducing energy consumption. Unlike the most efficient gas boilers (A-rated), which operate at around 90% efficiency (1:0.9 energy-to-heat ratio), heat pumps can achieve efficiencies of up to 300% or more (1:3 or higher energy-to-heat ratio). This efficiency gain makes heat pumps an essential part of the NHS decarbonisation strategy, helping to achieve the ambitious target of an 80% reduction in emissions between 2028 and 2032, on the path to full Net Zero by 2040.1
However, heat pumps alone are not the solution. Heat networks — which distribute heat from a centralised source across multiple buildings — are playing an increasingly vital role in NHS decarbonisation. By integrating heat pumps within district heating networks, hospitals can achieve even greater energy savings, cut carbon, reduce reliance on fossil fuels, and enhance the resilience of their heating infrastructure.
Recognising the scale of the challenge, the UK government has launched a £500 m framework to help decarbonise NHS buildings.3 This investment covers a range of interventions, including air-source and ground-source heat pumps, electric heating solutions, ventilation upgrades, and photovoltaic systems. However, while financial support is increasing, implementing these solutions effectively requires a strategic and technical shift in how NHS estates approach heating and cooling.
As a result of their exceptional efficiency, heat pumps are central to the NHS’s heating decarbonisation strategy. Their ability to harness low-grade heat from the environment, and upgrade it into a useful form for heating buildings and producing hot water, is crucial for NHS hospitals looking to lower their energy consumption while maintaining the heating demands of complex healthcare environments.
De-steaming of heating systems
Traditionally, hospitals have relied on high-temperature gas-fired heating systems, often running at 85°C or more, to support sterilisation, heating, and hot water production. A key challenge for decarbonisation is that air-source heat pumps alone cannot always reach these high temperatures, leading many NHS Trusts to de-steam their heating systems as part of the transition. This means redesigning heating infrastructure, not just replacing one technology with another.
Cooling has traditionally been seen as separate from heating in NHS buildings, but integration offers a significant opportunity to cut emissions further. Heat pumps generate waste cool as a by-product, while traditional chiller systems produce waste heat. In many hospitals, this waste energy is simply expelled into the atmosphere. However, by connecting these systems, hospitals can capture and redistribute energy more efficiently.
At Carrier, we’ve seen hospital chillers that are pumping hot air into the atmosphere while the heat pumps are pumping cold air into the atmosphere. By changing to a water-based system, we can connect them both and combine these thermal waste streams in a total energy system. This can deliver serious efficiency benefits, but requires a real understanding of system integration and technology interplay.
This ‘ambient loop’ approach — where heating and cooling systems are integrated into a shared energy exchange network — offers significant efficiency gains and cost savings. Such integration ensures that every unit of energy used within an NHS facility is maximised, rather than being wasted.
For heat pumps to deliver their full decarbonisation potential, hospitals need to take a whole-building approach rather than simply swapping out old boilers for new systems. The NHS has historically adopted a piecemeal approach to energy efficiency, replacing boilers as they fail. However, the transition to heat pumps is not just about swapping technology, but instead about rethinking how buildings and entire estates function.
For instance, you can’t just take out a gas boiler and replace it with a heat pump of the same size. NHS estates have changed over time — lighting is now based on LEDs, energy usage has shifted, and what hospitals do inside their buildings has evolved. We need to understand the building’s current energy demand before we change anything.
This shift requires a data-first strategy, where hospitals first analyse:
- How energy is used within the building.
- How demand has evolved over time.
- Where waste energy can be recovered and reused.
- How new technologies like heat pumps can be integrated with existing systems.
By reassessing energy demand, improving building fabric, and optimising insulation, hospitals can design heating and cooling systems that match modern requirements, rather than replicating outdated gas boiler configurations.
Boiler replacement and the interplay of sustainable technologies
The new focus on managing hospital estates as total energy systems brings to the fore the issue of the interoperability of equipment and systems. Heat pumps do not operate in isolation — they must work with and alongside other sustainable technologies, such as heat networks, waste heat recovery, battery storage, and renewable energy generation.
What began as just a boiler replacement scheme and the installation of heat pumps is now much more than that. It’s about a whole-site approach. This requires a much deeper understanding of the thermodynamic principles at play, and how technologies interact.
To achieve Net Zero, therefore, NHS hospitals must move away from short-term fixes, and instead implement long-term, scalable strategies that integrate:
- Heat networks for district-wide efficiency.
- Energy storage to balance supply and demand.
- Solar PV and renewable electricity to power heat pumps sustainably.
- Waste heat recovery to prevent energy losses.
This multi-technology, whole building/estate approach ensures that heat pumps do not just replace gas boilers, but operate within a fully optimised, future-proofed system.
From this it can be seen that, as the NHS works towards achieving Net Zero by 2040, individual building upgrades alone will not be enough. To reach the necessary scale of emission reductions, the NHS must adopt district-wide solutions that provide sustainable heating and cooling across multiple sites. Heat networks — also known as district heating systems — are one of the most promising strategies for achieving this goal.
Heat networks supply heat from a central source to multiple buildings via a network of underground pipes carrying hot water. Instead of relying on individual gas boilers distributed across buildings or estates, NHS facilities connected to a heat network can receive heat from a large-scale centralised source, such as a high-efficiency heat pump, waste heat from industry, or renewable energy systems.
Several key advantages
For NHS hospitals, where energy demand is high and 24/7 reliability essential, heat networks offer significant advantages:
- Increased efficiency — centralising heat production allows for greater efficiency by reducing energy waste and optimising heating loads across multiple buildings.
- Lower carbon emissions — heat networks enable hospitals to transition away from fossil fuels more effectively, integrating heat pumps and renewable energy at scale.
- Cost savings and infrastructure benefits — by sharing heating infrastructure across multiple sites, NHS Trusts can reduce operational and maintenance costs while avoiding the disruption of replacing individual boiler systems in each building.
A heat pump-based heat network takes this concept a step further by using a large-scale heat pump as the primary heat source. Instead of each building relying on its own gas-fired heating system, a central heat pump extracts heat from the air, ground, or water, and distributes it efficiently across a network of connected buildings.
A standalone heat pump constantly ejects hot air back into the atmosphere as part of its process — just like an air-source chiller expels heat. Operating as part of a heat network, however, that waste heat produced can be captured and reused efficiently. Instead of wasting energy, the system balances heating and cooling loads to maximise efficiency. This energy ‘recycling’ approach ensures that waste heat from cooling systems can be repurposed to support heating demands, making the entire network more efficient and sustainable.
For NHS estates, heat networks provide a scalable and future-proof way to transition away from fossil fuels. However, the size and design of the network play a crucial role in maximising efficiency. To give an illustration of the principle in relation to residential homes: If you take 100 houses, each with a six kilowatt boiler, that’s 600 kilowatts of total heating capacity. In reality, however, the demand across all those houses will never peak at the same time — so a shared heat network can operate at a much lower total capacity. The same applies to hospitals; a single centralised energy centre can be much more efficient than multiple standalone systems.
In the NHS, heat networks can be implemented at different scales:
- On a single NHS site — a ‘campus network’, where multiple hospital buildings share heating from a central energy centre.
- Across an NHS Trust — a district heating system serving multiple hospitals or healthcare sites within a Trust.
- At city scale — connecting NHS sites to large-scale urban heat networks, powered by heat pumps, waste heat, or other low-carbon sources.
Case study: OPDC heat network and Central Middlesex Hospital
A ‘real-world’ example of heat networks in action is the Old Oak and Park Royal Development Corporation (OPDC) heat network in London, which is expected to deliver 95 GWh of heat across five phases between 2026 and 2040.4 This system will capture waste heat from local data centres, initially at 30-40 °C, and upgrade it to 65 °C for distribution across the district. One of the key beneficiaries of this system will be Central Middlesex Hospital.
By tapping into this low-carbon heat source, the hospital will reduce its reliance on gas boilers, requiring only minor on-site heating upgrades to meet its operational needs. This integrated heat network approach demonstrates how hospitals can reduce carbon emissions while maintaining reliability. Even after de-steaming, many NHS buildings still operate at 85 °C for heating. A heat network like OPDC will allow hospitals to meet their high-temperature heating requirements while relying on a more sustainable source.
This example illustrates how heat networks combined with heat pumps offer a flexible pathway to decarbonisation — without requiring a complete overhaul of legacy heating systems.
For NHS Trusts looking to implement heat networks, a key consideration is how they will integrate with existing heating and cooling infrastructure. In some cases, heat networks can fully replace gas-fired heating systems, but in others, hospitals may still need to retain on-site back-up capacity. Even when part of a district heat network, hospitals are critical services. They must have back-up heating in case of supply failures. So, while heat networks can reduce the need for on-site equipment, NHS estates may still need localised heat pumps or back-up boilers for resilience.
The best approach depends on each hospital’s energy profile, available grid capacity, and the scale of the heat network. In many cases, a hybrid strategy — where heat networks provide the primary heating supply, with heat pumps handling peak loads or backup capacity — is the most practical solution.
Despite their benefits, heat networks are not without challenges. Key issues include:
- Upfront investment — installing a heat network requires significant capital expenditure, although long-term savings often outweigh the initial costs.
- Regulatory barriers — the UK’s heat network zoning policy, which mandates that buildings in designated areas connect to district heating, is still evolving.
- Tariff structures and pricing — NHS Trusts must ensure that heat network tariffs are cost-effective and transparent, preventing monopoly pricing by network operators.
Regulatory frameworks are improving, but NHS Trusts must carefully evaluate the financial and operational models of heat networks before committing to large-scale deployments.
Scaling heat networks across the NHS
The NHS is already taking steps to expand its use of heat networks, supported by funding initiatives such as the Green Heat Network Fund,5 and the Public Sector Decarbonisation Scheme (PSDS).6
For hospitals looking to integrate heat networks, the key steps include:
1 Conducting a feasibility study — assessing heat demand, available infrastructure, and potential integration with existing heating systems.
2 Evaluating heat sources — determining whether the network will be powered by heat pumps, waste heat, or renewable energy.
3 Ensuring regulatory compliance — working with government and local authorities to align with heat network zoning policies.
4 Integrating on-site backup systems — designing a hybrid solution that balances network supply with on-site resilience.
As NHS Trusts continue their Net Zero journey, heat networks will play a critical role in ensuring that hospitals, clinics, and other healthcare facilities can access low-carbon heating at scale. By integrating heat pumps, heat recovery, and renewable energy, the NHS can transition to a resilient, cost-effective, and sustainable energy model for the future.
To get the NHS to Net Zero by 2040, the role of manufacturers like Carrier is evolving beyond simply supplying equipment. Traditionally, manufacturers became involved at later stages of a project — typically during the procurement and installation phase. However, given the complexity of heat pump and heat network integration, manufacturers are now playing a more active role from the outset, providing technical guidance, system optimisation, and long-term monitoring.
Early-stage involvement is the key to success
One of the biggest challenges in NHS decarbonisation is ensuring that heating and cooling systems are designed correctly from the start. Manufacturers need to be involved at the concept stage, not just when the project is going out to tender. The reality is that no one understands the capabilities and operation of heat pumps better than the manufacturers. If brought in too late, mistakes can be made in system design that affect performance and efficiency.
Heat pumps are not a ‘one-size-fits-all’ solution. The efficiency and effectiveness of a system depends on multiple factors, including:
- The type of heat pump used (air-source, water-source, ground-source).
- The operating temperatures required (high-temperature retrofits vs. low-temperature new builds).
- Integration with existing systems (e.g. heat networks and back-up boilers).
By engaging with NHS Trusts and consultants early, manufacturers can help shape system designs to ensure that decarbonisation strategies are practical, cost-effective, and future-proofed.
Once installed, heat pump and heat network systems require ongoing performance monitoring to maintain efficiency and reliability. Without proper oversight, systems can underperform, leading to higher energy costs and lower-than-expected carbon savings. We need to move away from a ‘fit and forget’ mentality. Heat pump systems require ongoing monitoring, optimisation, and future planning. Without this, hospitals risk efficiency losses, and in a worst-case scenario, they may not achieve the carbon savings they set out to deliver.
Key areas where manufacturers can support NHS Trusts include:
- Real-time performance tracking — ensuring that systems are operating at peak efficiency.
- Predictive maintenance — identifying potential failures before they impact hospital operations.
- Long-term system adaptation — optimising heating and cooling infrastructure as hospital energy needs evolve.
By working closely with NHS estates teams, manufacturers can ensure that HVAC systems are delivering on their Net Zero potential.
One of the biggest barriers to heat pump adoption in the NHS is the challenge of accurately evaluating financial and operational benefits. While heat pumps offer long-term cost savings, the upfront capital expenditure can be a hurdle. When NHS Trusts evaluate energy solutions, they rely on modelling and performance data, but the quality of this data can vary significantly. A project might be supported by the best consultant in the world, but if the data being used is outdated or merely theoretical, the results will be flawed. This is a huge issue when it comes to energy modelling.
To ensure accurate financial forecasting, NHS Trusts should:
- Use up-to-date industry standards — for example, heat pump performance should be evaluated using EN 14511-3:2022, which accounts for part load and defrost conditions.6
- Validate manufacturer performance claims — different manufacturers use different methodologies to report efficiency, making direct comparisons difficult. Eurovent Certification offers a performance validation programme for heat pumps through its Eurovent Certified Performance (ECP) programme. This programme verifies various performance characteristics, including capacity outputs, to ensure transparency and allow for fair comparisons between manufacturers.
- Look beyond initial cost — the total cost of ownership (TCO), including energy savings, maintenance, and system lifespan, is a better indicator of long-term value.
Another challenge in NHS decarbonisation is that procurement processes are often driven by lowest-cost tenders, rather than prioritising long-term performance. There is always a tension between cost and quality. You might find a consultant that is cheaper, but in this scenario, cheaper is rarely better. The NHS needs to look at evidence of real-world system performance before selecting partners. By focusing on quality and long-term performance over initial cost, NHS Trusts can avoid falling into this trap, ensuring that heat pumps and heat networks deliver the expected carbon savings and cost reductions over their working life.
Future innovations in heat pump and heat network technology
While today’s heat pump and heat network solutions are already delivering major efficiency gains, continuous innovation will play a crucial role in further decarbonising NHS estates.
One of the biggest challenges for the NHS is that many existing buildings still require water for heating at 85 °C, which is beyond the typical capabilities of standard heat pumps. At Carrier, we’re pioneering rapid advancements in high-temperature heat pumps, which will allow hospitals to transition away from gas-fired systems without needing expensive infrastructure upgrades.
As manufacturers continue to refine higher-output heat pump technology, this will open up more opportunities for NHS sites to transition to low-carbon heating. Refrigerant technology is another area of innovation, with manufacturers developing low-GWP alternatives to reduce environmental impact. As regulations tighten around high-GWP refrigerants, NHS Trusts will need to ensure that their systems are future-proofed against legislative changes.
One of the most exciting developments is the shift towards more intelligent, data-driven system integration. Future heat pump and heat network technologies will:
- Optimise energy use in real time based on hospital demand and external conditions.
- Automatically balance heating and cooling loads, reducing energy waste.
- Enable greater connectivity with renewable energy sources and energy storage solutions.
The big shift isn’t just in technology — it’s in how we integrate and manage energy systems. That’s why manufacturers are moving towards a holistic approach, working closely with NHS Trusts from the start.
A collaborative future for NHS decarbonisation
The NHS’s Net Zero commitment is ambitious, but achievable — with the right technologies, expertise, and strategic planning. Heat pumps and heat networks will be at the heart of this transformation, but their success will depend on:
- Early engagement with manufacturers, ensuring that system designs are optimised from the outset.
- High-quality data and modelling, allowing NHS Trusts to accurately forecast financial and operational benefits.
- Ongoing monitoring and system optimisation, ensuring that heat pumps and heat networks deliver their full potential.
Manufacturers, like Carrier, are committed to working in partnership with the NHS, not just as equipment suppliers, but as long-term decarbonisation partners. Carrier is currently working with several major NHS Trusts and Health Boards around the country to support their strategic plans to decarbonise estates. Crucially, we need to move beyond the traditional hierarchy of procurement, installation, and operation. By collaborating from the start, engaging with consultants, and educating NHS teams, we can create truly integrated energy solutions that help the NHS reach Net Zero by 2040.
References
1 Delivering a ‘Net Zero’ National Health Service. NHS England and NHS Improvement. October 2020. https://tinyurl.com/bdc4ec8n.
2 Williams M. A Net Zero NHS: How heat networks can help transform our health service. 10 October 2024. https://gemserv.com/our-thoughts/a-net-zero-nhs-how-heat-networks-can-help-transform-our-health-service/.
3 Grant P. Winners revealed as NHS plans to spend £500m on decarbonisation. Construction Enquirer. 13 January 2025. https://tinyurl.com/3fzyt7c6.
4 OPDC pioneers innovative, money-saving technology as one of England’s first Heat Network zones. Mayor of London / London Assembly. 29 October 2024. https://tinyurl.com/yrszawbn.
5 Green Heat Network Fund: guidance on how to apply. Department for Energy Security and Net Zero. 4 March 2022. https://tinyurl.com/2jpkveez.
6 Public Sector Decarbonisation Scheme. Department for Energy Security and Net Zero. 1 October 2020. https://tinyurl.com/uzw6adje.
7 24/30487361 DC. BS EN 14511-3:2022/A1 Air conditioners, liquid chilling packages and heat pumps for space heating and cooling and process chillers, with electrically driven compressors. – Part 3: Test methods. bsi. 15 February 2024.