London Power Tunnels: an up-close look at South London’s energy transformation

Earlier this month, National Grid welcomed members of the All-Party Parliamentary group for Infrastructure (APPGI) to New Cross to see the London Power Tunnels – the construction project being built to rewire South London.

National Grid’s Mark Lissimore, director of electricity transmission projects, gave visitors an overview of the current electricity distribution network and the steps to meet the government’s net zero ambitions for 2030 and 2050.

London Power Tunnels project director Onur Adeymir then told attendees about the project, challenges the team has overcome, and how they’ve kept the billion-pound project on time and within budget.

The visit included a trip down the shaft and into the New Cross tunnel to see, first-hand, the sheer scale of the project and the operations needed to deliver it.

What is the London Power Tunnels project and why is it critical to the capital?

In Spring 2020, National Grid started a seven-year project to rewire South London via deep underground tunnels.

This vital work will help keep Londoners connected to safe and reliable electricity supplies.

Most of South London’s current electricity supply transmits through underground cables just below the road surface. Many are nearing the end of their useful life.

Housing new electricity cables in deep underground tunnels has several benefits. There’s less disruption during construction to traffic, residents, and businesses.

Likewise, future repairs and maintenance will cause minimal disturbance. And the tunnels can accommodate additional cables to meet future demand.

What infrastructure is needed to deliver London Power Tunnels?

In total, National Grid is constructing 32.5km of 3m diameter tunnels deep below the road network between Wimbledon and Crayford. These will carry high-voltage electricity cables.

National Grid needs to build six new shafts and headhouses at key locations across the route to provide access and ventilation for the tunnels.

The headhouses will cover the shafts once the tunnel is built.

How has the London Power Tunnels project progressed so far?

National Grid has made significant headway on the project, with two of four tunnel-boring machines (TBMs), Christine and Caroline, ‘breaking through’ at the Eltham and Wimbledon sites. They’ve completed 7km and 5.7km journeys respectively.

Most recently, in April 2023, the TBM at King’s Avenue broke through. With this milestone achieved, the TBM is being dismantled and removed from the tunnels by a crane.

The TBM tunnelling towards Eltham from New Cross is likely to break through this autumn.

How the London Power Tunnels project is delivering National Grid’s net zero goals

In 2021, National Grid made a corporate commitment to “ensure that [construction] activities are carbon neutral by 2025/26” and stated: “To achieve this, we are looking to reduce or offset all the carbon we use or generate in our construction projects.”

To achieve this commitment, National Grid committed to a 5% reduction in all carbon emissions, with a stretch target of 8% for the London Power Tunnels project.

The latest monitoring of carbon reduction to date, including in the shafts, tunnels, and headhouses, measured a 21% reduction against the pre-project baseline.

This is equivalent to 25,250 tonnes of CO2 – equal to 115,894,776 miles travelled by the average UK car.

Achieving a 21% carbon reduction

The project has diverted 99.98% of project waste away from landfill.

New eco-friendly, low-emissions diesel generators have been used throughout the project.

Working with substation contractors, National Grid has been deploying new technology to eliminate the use of the potent greenhouse gas Sulphur Hexafluoride (SF6) in equipment insulation, minimising the project’s environmental impact.

And in May, National Grid completed the world’s largest-ever continuous pour of cement-free concrete to fill the 55m-deep tunnel drive shaft at the Hurst substation in South London.

The concrete reduces carbon by around 64%, saving an estimated 111kg of CO2 per cubic metre poured. The 736,000-litre pour at Hurst saved an estimated 82 tonnes of CO2.

The London Power Tunnels project is due to be completed and fully operational in 2027. Learn more about the project.

The ICE supports the APPGI in highlighting to government and industry the importance of economic infrastructure in the UK. Find out more.

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