Lessons from Copenhagen: What London can learn from the Danish heat network approach

London’s heat networks are central to meeting net zero commitments and to unlocking local, more affordable and more sustainable sources of heat. If cities want a preview of what ‘heat network at scale’ really looks like, Copenhagen is a good place to start. Denmark has been building and refining district heating for more than a century – and the results are written into the fabric of the capital.

• A 123-year head start (and counting): Denmark’s first district heating system was developed in 1903.
• Today the network transports 85% CO₂-neutral heat each year to half a million people – reaching around 98% of the city.
• 3,000 kilometres (2,000 miles) of pipes – spanning the same distance as Brentford to Dartford, and Loughton to Leatherhead.

Copenhagen’s response to the climate crisis is defined by its quietly co-ordinated infrastructure. Homes stay warm through a shared heating network, business districts are cooled with seawater, heavy rainstorms are channelled into green parks that double as flood protection and waste is converted into energy – with carbon captured rather than released. Much of this system is largely hidden beneath the streets, but its benefits are clear in the city’s design.

At the heart of Copenhagen’s approach lies its district heating network, which at 180km long and serving 28 boroughs, covers about 98% of the city. In terms of geographic scale, it spreads across an area with boundaries similar to the M25 – overlaid (in red opposite) on to a map of London the Copenhagen network stretches from Dartford in the East to Brentford in the West, and from Loughton in the North to very nearly Leatherhead in the South.

Hot water, produced by combined heat and power (CHP) plants, waste-to-energy facilities, and large heat pumps, is distributed efficiently to homes and businesses across the city. During the summer, a parallel district cooling network utilises free cooling from seawater, removing any need for commercial buildings to run air conditioning, making the whole process much more efficient and planet friendly.

Denmark’s heat network strategy has evolved over more than a century, adapting to technological advances and shifting political priorities. Its first system established in 1903, used an incineration plant to generate electricity and steam which, via tunnels, supplied a hospital, children’s home and a ‘poorhouse’. Today the city owns the heat main through a not-for-profit company and suppliers effectively buy heat from that in order to supply their customers.

Copenhagen’s district heating draws from a wide range of energy sources – biomass, waste incineration, geothermal, surplus industrial heat and, increasingly, renewables such as wind and solar.

The country is also committed to ambitious carbon capture goals and aims to diversity its energy inputs, reducing reliance on external biomass supplies and fossil fuels. Innovative projects such as CopenCapture, with its famous ski slope roof is developing a carbon capture and storage project with a target of capturing 400,000 tonnes of CO₂ each year.

While Copenhagen sets a benchmark, other European cities such as Malmö and Berlin are also pioneering innovative heat network solutions.

In Malmö E.ON’s 720km heat network already delivers enough heat each year to power 95% of the city’s residents. The system, a relationship between E.ON and the municipality, has evolved over decades. From fossil fuels in the 1950’s, transitioning to natural gas and waste-to-energy by 2008 to today’s integrated geothermal, waste heat recovery (including from sewage) and low temperature distribution. Around 65% of the heat now comes from the city’s publicly owned energy-from-waste plant on the outskirts, connecting to the city centre via two 15km heat mains. In addition, we use waste heat from the city’s sewage treatment works which is upgraded using 40MW of heat pumps, further enhancing the system’s efficiency and sustainability.

In Berlin, to the east of the German capital in Schöneweide, E.ON is harnessing the power of the River Spree to feed a 180km heat network. The project which supplies around 80,000 apartments and commercial buildings, with large river source heat pumps cutting emissions by around 14,000 of tonnes of CO₂ each year.

For London there is ample opportunity to draw upon a diverse range of international experiences as it shapes its own approach to sustainable urban heating. 

Copenhagen’s strategic heat main offers several valuable lessons:

Holistic planning: London can benefit from a city-wide strategy that links heat, cooling, and renewable energy sources, rather than relying on piecemeal, building-by-building or even borough-by-borough solutions.

Diverse energy sources: Integrating waste-to-energy, renewables, and surplus industrial heat would improve resilience and reduce carbon emissions.

Large-scale heat storage: Investing in large scale pit storage which is common in Denmark and underground heat storage could help London balance energy needs.

At our Citigen energy centre in the heart of the square mile, E.ON has already laid the groundwork for a connected and sustainable future. With a district heating network of 12km and home to one of the world’s largest urban heat pump retrofits, the site is already cutting the City’s emissions by 5,000 tonnes a year. Proof that even in one of the most complex urban environments in the world, heat can be captured, re-used, and redistributed.

Denmark’s approach shows how careful planning, flexibility, and linking heat networks to broader city goals can help. For London, embracing these lessons could help the city reach its net zero goals quicker, cut energy costs, and improve quality of life. By learning from global leaders, London can design a heat network tailored to its needs, supporting the fight against climate change.