Waste heat, wild potential

We tend to think of energy as something visible: the turning blades of a wind turbine, or solar panels on a rooftop. But some of the most powerful solutions in our energy transition are hiding in plain sight – in the very infrastructure that keeps our cities moving.

Significant amounts of heat are lost every day from data centres, factories, train tunnels and even sewers. Often, this heat is simply released into the air or absorbed by the ground – invisible and unnoticed.

Yet with the right technology and planning, this ‘waste’ heat could be recovered and repurposed, helping to reduce emissions, increase efficiency and provide low-carbon warmth to thousands of homes and businesses.

The data centre dilemma – and opportunity

Modern cities run on data. Behind every online search, cat video stream or cloud-based app is a data centre – the digital engine room of our lives. But these vital facilities come with a growing energy demand. In fact, one proposed data centre in the UK could produce five times the emissions of Birmingham Airport.

Currently, the UK’s 500 data centres account for around 2.5% of national electricity consumption – a figure expected to rise to 6% by 2030.

Crucially, most of the electricity used to power servers is ultimately converted into heat. Without intervention, that heat is expelled into the environment – causing already overheated cities to become even warmer. But what if, instead of discarding it, we put it to use?

That’s where we see real potential. To unlock it, we’re calling for action: finalising the Heat Networks Market Framework to give investors the confidence to back these projects. That means making heat network connections mandatory in designated zones, limiting exemptions, and reforming the UK Emissions Trading Scheme (UK ETS) to mandate and reward the use of waste heat. Targeted infrastructure funding will also be key to turning this vision into reality – benefiting consumers, cities and investors alike.

Turning excess into access: harnessing heat at Silvertown

In East London’s Silvertown, we’re putting this idea into practice. As part of a major regeneration project with our partners Lendlease, our innovative ectogrid™ system will capture heat from nearby data centres and redistribute it through a local network – ultimately providing more than 6,000 homes and businesses with low-carbon heating and cooling.

It’s a new way of thinking about energy: using the by-products of our digital lives to support the energy needs of entire neighbourhoods.

London’s hidden heating systems

Silvertown isn’t the only example. In the heart of the City of London, we’re supporting the Mayor’s drive to decarbonise heat with a 22km network of heating and cooling pipes connected to our Citigen energy centre.

Citigen combines deep geothermal boreholes, high-efficiency heat pumps, and real-time digital controls to turn the energy beneath the city into sustainable warmth – serving iconic buildings such as the Guildhall, the Barbican, and the Museum of London.

It’s a powerful demonstration of how existing infrastructure can be repurposed to deliver low-carbon solutions - and at scale.

Power from the unlikeliest of places

But why stop at data centres?

We're capturing warmth from industrial sites, supermarket fridges, Tube tunnels beneath our feet – even sewers have a role to play.

Working with Severn Trent Water and Horiba MIRA, we’re recovering heat from waste water (near Coventry), which holds a year-round temperature of up to 20°C. A closed-loop heat exchanger and a heat pump system extract that warmth and transfer it to clean water networks to heat buildings – all without the two systems ever mixing.

Elsewhere, we’re exploring how to move waste heat from industrial areas further down the Thames and transport it upriver using floating thermal ‘batteries’ – specially designed containers that allow heat to travel by barge rather than by wire.

Rethinking how cities stay warm – and the policy shift behind it

As cities strive to decarbonise, heat networks are becoming a vital part of the transition, especially in dense urban areas with access to waste heat.

These networks distribute heat through insulated pipes and enable energy to be shared efficiently between buildings and communities. And governments are starting to mandate their use.

In Germany, new legislation now requires the reuse of waste heat, while the EU’s Data Centre Emissions Reporting Act (2024) is pushing for greater transparency and accountability in the sector. Here in the UK, local authorities are increasingly exploring how to connect large-scale producers of waste heat — such as data centres or refrigeration hubs — with residential developments and public infrastructure.

A smarter, cleaner future, powered by what we already have

As the pressure to reduce emissions grows, cities must rethink not only how they generate energy – but how they use and reuse it.

If we can recycle the heat that’s already there, we can drastically reduce the energy we need to generate in the first place. In fact, London already wastes enough heat to meet almost 40% of its heating demand.

Whether it’s heat from servers, train tunnels, or waste water pipes, we’re proving that the energy we need is often already here. It just takes the right systems to harness it – and a willingness to see potential in unexpected places.