National Grid launches North West London Upgrade project to strengthen electricity network and support future growth

National Grid has launched its North West London Upgrade (NWLU) project, a major investment designed to strengthen the electricity transmission network, support future growth and unlock new connections across North West London and surrounding areas.

Spanning from Sundon substation in Bedfordshire to Elstree substation in Hertfordshire, and on to St John’s Wood substation in London, the complex programme includes new and upgraded substations, new cables, and reinforcement of existing overhead lines.  

Together these works will increase network capacity and strengthen the resilience of electricity supplies across the region, as well as helping to keep energy bills down by reducing constraint costs.

The investment will also play a vital role in supporting economic growth across North West London as electricity demand rises, enabling new data centre connections while making sure homes, businesses and digital industries have the reliable power they need now and in the future.

The project adds to National Grid’s portfolio of ongoing work across the capital, which also includes London Power Tunnels 2 (LPT2) and the North London Reinforcement (NLR) scheme.

The NWLU programme involves:

• upgrades to Sundon substation in Bedfordshire;
• reconductoring the 35km Sundon–Elstree overhead line route;
• extending the existing Elstree gas insulated switchgear (GIS) substation;
• construction of the new Letchmore Heath GIS substation adjacent to Elstree;
• installation of a new 400kV cable circuit in the existing Elstree–St John’s Wood tunnel;
• upgrades to the Elstree–St John’s Wood tunnel and headhouses;
• reinforcement of the existing St John's Wood substation.

Works on the route between Sundon and Elstree will see over 200km of overhead line upgraded.

Alongside the overhead line works, 60km of new cable infrastructure will be installed within the existing Elstree–St John's Wood tunnel. Stretching for more than 20km, the tunnel already carries the longest alternating current (AC) transmission cables on the England and Wales transmission network, and was originally designed in the early 2000s to accommodate an additional cable circuit if needed in future.

In Hertfordshire, the project will extend the existing 400kV Elstree GIS substation and build the new 132kV Letchmore Heath GIS substation next door to connect five new data centres – equivalent to 1GW of demand.

Laing O’Rourke has been appointed to deliver substation works at Letchmore Heath, Elstree and St John’s Wood; HMJV will deliver the cable installation and tunnel upgrades; Hyundai Electric will supply and install major electrical equipment like transformers, while Siemens Energy is responsible for shunt reactors at Elstree substation.

Joe Senior, project director at National Grid, said:

“The North West London Upgrade is a nationally significant investment that will strengthen the electricity network, unlock new connections, support regional economic growth and help keep long term energy costs down for consumers.

“Working closely with our delivery partners and supply chain, we're bringing together substations, cables and tunnels, and overhead line reinforcement in a single programme to deliver the infrastructure needed to power future homes, businesses and digital industries as electricity demand rises.”

Raj Kundan, HMJV project director, said:

“HMJV are proud to continue supporting National Grid in the delivery of critical national energy infrastructure, bringing our cutting-edge solutions and ‘One Team, One Spirit’ approach. Our team look forward to working in collaboration with National Grid and the enterprise partners to leave a positive legacy for all those connected with the scheme.”

Peter Lyons, Managing Director of Laing O’Rourke’s Europe hub, said:

“This work builds on Laing O’Rourke’s partnership with National Grid, having been appointed as construction partner to The Great Grid Upgrade, Wimbledon Asset Replacement, and Margam and Port Talbot substations. We will be utilising our digital tools to enable our teams to deliver safely and efficiently on site. These critical upgrades are just part of our ongoing work with National Grid to provide more secure energy for the UK.”

In line with government guidance, communities near the new Letchmore Heath substation will be eligible for up to £530,000 to be spent on projects that improve the social, economic and environmental wellbeing of the community and deliver long term local benefits.

Further information about the North West London Upgrade can be found on the project website.