Discover how one of the UK’s first zonal heat networks could change the way London’s landmark buildings are heated – and set a blueprint for city-scale decarbonisation.
In one of the most historic and energy-intensive parts of London, a new project is reimagining how some of the city’s most iconic buildings are heated.
Set to become one of the UK’s largest heat networks, SWAN (South Westminster Area Network) may supply low-carbon heat to up to 300 buildings and over 1,000 customers across the heart of London, including landmarks such as the Houses of Parliament, Somerset House and the National Gallery.
SWAN is one of the first projects to pilot the UK’s new heat network zoning approach – focusing on areas with high heat demand and strong potential for low-carbon supply.
Commissioned by the Department for Energy Security and Net Zero (DESNZ) in 2020, we led the early development of this trailblazing scheme – from feasibility and system modelling through to business case, funding and procurement.
Our work spanned district heating services, stakeholder engagement, project management, building engineering, civil and marine infrastructure, and hydrology.
Designed to deliver over 300 gigawatt hours (GWh) of low-carbon heat each year, the network is expected to cut emissions by up to 92 per cent – compared to current levels – in the buildings it will supply.
SWAN reached a major milestone in 2024 with the appointment of the SWAN partnership, a joint venture made up of Vital Energi and Hemiko, investing in the network.
While construction is set to begin in 2026, the scheme is already serving as a national blueprint – helping DESNZ and local authorities shape how future heat networks are planned, funded and delivered across the UK.
‘The most significant heat network scheme designed in the UK’
SWAN stands out not just for its size, but for how it will reuse energy already moving through the city. The network can harness waste heat generated by the River Thames, London Underground, sewer systems and Transport for London (TfL) ventilation shafts, as well as energy drawn from London’s underground aquifer system (the city’s main groundwater resource).
These energy sources will be connected through a newly integrated system of underground pipes and, where possible, will make use of existing infrastructure and heat networks. This zonal approach reduces the need for new plant and will create a cleaner, more resilient energy network – ready to grow as demand increases.
With no visible rooftop equipment required, the scheme’s design will protect Westminster’s historic streetscape while supporting large-scale heat decarbonisation in one of London’s most complex urban environments.
The scale and complexity of SWAN make it the most significant heat network scheme designed in the UK. Once operational, it is expected to reduce carbon emissions in Westminster by 75,000 tonnes annually.
Our district energy market sector lead, Channa Karunaratne, said: “The size and ambition of SWAN demonstrate how to drive decarbonisation at a city-scale, and it is a trailblazer for how our cities can operate more sustainability.
“Westminster is one of the most recognisable locations in the world and through SWAN, the political engine of the UK is going to be supplied almost entirely with low-carbon heat for the first time.”
Trailblazing a new model to deliver heat networks
From the outset, we worked closely with DESNZ and partners to help develop and test a new approach to planning, funding and delivering heat networks at scale.
Working closely with commercial advisors HermeticaBlack, financial advisors Asteros, and legal advisors Burges Salmon, our technical modelling and system simulations demonstrated that the scheme was both technically achievable and commercially viable, providing the foundation for a robust business case for investment.
This work helped shape a delivery model now being replicated across the UK – aligning the technical, commercial, legal and delivery aspects of large-scale heat network projects, and supporting local authorities in securing joint venture partners to take them forward.
Through this process, a joint venture comprising two delivery partners was appointed in 2024, backed by £21 million from the Green Heat Network Fund. By helping DESNZ formalise this approach through SWAN, we’ve supported the creation of a standardised, replicable route to market – one that gives public and private partners the confidence to invest in large-scale, low-carbon heat.
SWAN stands out not just for its size, but for how it will reuse energy already moving through the city.
Securing early support and stakeholder buy-in
Given its scale and complexity, this project required early, strategic collaboration.
Drawing on insights from our work across Whitehall, the Old War Office and the parliamentary estate, we supported DESNZ in securing backing from a wide network of stakeholders – including government departments, Westminster City Council, Business Improvement Districts and private asset owners.
This early support gave SWAN the credibility and momentum it needed to move forward.
A new era for low-carbon heat in the capital
SWAN is helping unlock a new chapter in the UK’s transition to clean heat.
As one of the first schemes to test the zonal model at city scale, it demonstrates how cities can move beyond pilot projects to deliver fully integrated heat networks – with the potential to cut carbon emissions, improve local air quality and support hundreds of green jobs across the capital.
From the outset, we’ve played a pivotal role in shaping the scheme’s vision, delivery model and business case. We’re proud that our work on SWAN has contributed to us winning the UK District Energy Association’s 2025 Heat Networks Advisor of the Year award.