Cities generate heat almost everywhere you look – from data centres powering your Wi-Fi to fridges in your local supermarket – yet most of it is wasted. In London alone, enough heat is thrown away each year to meet 38% of the city’s heating demand. Capturing even part of this through heat networks could warm homes, businesses and public buildings without needing to generate as much new energy. 

If you are in the City of London – where E.ON’s Citigen helps to heat, cool and power buildings – there is an active heat network beneath your feet. Tucked behind the façade of a listed building, Citigen supplies low-carbon heating and cooling through 12km of pipes to 28 buildings including the Barbican, Guildhall and JJ Mack building, cutting emissions by around 5,000 tonnes a year 

Citigen is an example of a heat network, while a heat zone is a wider designated area where heat networks are planned, prioritised and coordinated to connect multiple buildings to low-carbon heat over time. 

Rolling out heat zones at scale could be one of the UK’s strongest tools for lowering energy bills and cutting emissions. By shifting from global fossil-fuel markets to local low-carbon heat, the UK can build a more stable, resilient and affordable system. Investment would also create skilled jobs and support greener, more liveable cities. Heat zones represent the biggest change to our energy infrastructure for a generation and will require partnership across government, local authorities, businesses and communities to ensure their success 

Our new report sets out the lessons for the UK as we move towards heat zones, informed by our experience across Europe: 

1)         Heat Zones need scale
European cities show that planning at scale delivers better results. In Malmö, Sweden, large networks serve most residents, allowing neighbourhoods to plug in without repeated disruption. Scale boosts efficiency, investor confidence and the shift from fossil fuels to cleaner heat. 

2)         Heat Zones require access to low-carbon heat sources
Successful networks rely on local resources such as rivers, sewage or industrial heat. In the Square Mile, Citigen taps multiple sources, including geothermal energy from the London Aquifer. A 12 km pipe network supplies heating, cooling and electricity to homes, offices and heritage buildings like the Barbican and Guildhall. 

3)         The UK needs a more supportive regulatory environment
Replacing gas with heat networks requires major investment and stable regulation. Europe shows the value of clear long-term rules, supportive planning and predictable revenue models. Capital support and mechanisms narrowing the gap between electric heat pumps and gas can attract finance while keeping bills fair. 

4)         Coordinate infrastructure delivery to maximise benefit
Installing pipework can be disruptive, but also an opportunity to rethink streets. European cities often align heat-network construction with utility upgrades, cycle routes or greener walkways, reducing disruption and costs. 

5)         Support and incentivise customers to join the Heat Zone
A heat zone succeeds when a broad mix of buildings connect. European cities pair clear expectations with support such as energy audits, efficiency upgrades and bundled offers integrating solar or smart controls. 

6)         Harness Heat Zone investment to train and upskill
Heat zones create long-term jobs. European programmes link investment to apprenticeships and local supply chains. In the UK, this means working with colleges and training providers to build the workforce needed for the transition. 

As the UK prepares to deliver new heat zones, including in the City of London, it has the chance to turn wasted heat into a strategic asset and move rapidly from pilots to full-scale zones that cut bills, reduce emissions and future-proof our cities.