Solar Power and Waste Heat Set to Transform London Underground Energy Use

Transport for London (TfL) has outlined ambitious plans to integrate renewable energy and heat recovery into the London Underground, with solar power and waste heat set to play a growing role in how the network operates.

As part of its target to use 100% renewable electricity by 2030, TfL has announced it expects to generate around 65,000 megawatt hours of solar energy each year. This would account for a significant proportion of the energy used across the network—equivalent to roughly two-thirds of the Victoria line’s annual electricity consumption.

TfL, the largest single electricity user in the capital, currently consumes around 1.6 terawatt hours of electricity annually—similar to the usage of nearly 600,000 homes. To support its transition, it has partnered with SSE Energy Solutions to develop new solar farms that will supply power directly to the network, reducing reliance on the National Grid. One of the first confirmed sites for development is in Longfield, Essex, with further locations under consideration.

Lilli Matson, TfL’s Chief Safety, Health and Environment Officer, said locally generated renewable energy would not only help reduce pressure on the grid but also provide greater resilience against energy price fluctuations while delivering potential cost savings.

Alongside solar generation, TfL is continuing to expand its innovative use of waste heat from the Underground. A pioneering project in Islington is already using excess heat from Tube tunnels to supply heating and hot water to homes and community facilities.

The Bunhill 2 Energy Centre, built on the site of a disused Underground station, captures warm air from the Northern line via a large ventilation system. This heat is transferred to water, which is then distributed through a network of underground pipes to nearby buildings.

The scheme has already extended the existing district heating network, adding hundreds of homes and a school to the system. In total, the expanded network has the potential to provide low-carbon heating to more than 2,000 homes, alongside leisure facilities and other community buildings.

The technology also incorporates combined heat and power systems, generating electricity that can be used within the Underground network and nearby buildings. In addition, the system can be reversed during warmer months to help cool the Tube tunnels.

Mayor of London Sadiq Khan described the project as an example of the type of innovation needed to achieve the capital’s net zero ambitions. He emphasised the importance of collaboration between TfL, local authorities, and other partners in delivering sustainable solutions to the climate challenge.

Andy Lord, Managing Director of London Underground, highlighted the global significance of the initiative, noting that capturing and reusing heat from the Tube network at this scale is a world-first. He added that further research is underway to identify additional opportunities across the network.

The system works by extracting warm air from tunnels and passing it over water-filled pipes, slightly increasing the water temperature. Heat pumps then raise the temperature further to around 80°C, making it suitable for heating homes and buildings. The heated water is circulated through insulated pipe networks, where heat exchangers transfer it into local heating systems.

For residents connected to the network, the benefits include lower heating costs and reduced carbon emissions. The scheme is expected to cut CO2 emissions by around 500 tonnes annually while also lowering energy bills compared to traditional heating systems.

The Bunhill project represents a collaboration between Islington Council, TfL, and the Mayor of London, and is widely seen as a blueprint for similar schemes in other cities.

Together, TfL’s solar energy programme and heat recovery initiatives demonstrate how large urban transport networks can play a central role in the transition to cleaner, more sustainable energy systems—delivering benefits not just for passengers, but for communities across the capital.