A new energy centre using heat from Northern Line Tube tunnels can now provide warmth and hot water to 1,350 Islington homes.
Islington Council and Transport for London claim nothing like Bunhill 2 has ever been done before.
The energy centre in City Road connects an additional 550 additional homes and Moreland Primary School onto Islington's existing district heating system, which already serves 800 households plus Iron Monger Row Baths and Finsbury Leisure Centre. The remains of City Road station, which closed in 1922, now contain a huge fan which extracts warm air from the tunnels.
This is used to heat water that's then pumped to buildings in the neighbourhood through a new 1.5km network of underground pipes. The centre's combined heat and power technology means electricity is also fed into the London Underground network and an adjacent tower block, powering its communal lighting and lifts. The underground fan can be reversed to help cool the Tube tunnels during the summer.
The extension to the Bunhill Heat and Power district heating network is a collaboration between Islington Council, TfL and the mayor of London.
It was funded by Islington Council, which owns and runs the network, and a grant from the European Union's CELSIUS project.
Mayor of London Sadiq Khan said: "It's great to see this highly innovative project up and running, recycling waste heat from the Tube to provide a low-carbon, affordable way of heating local homes and businesses."
Islington's environment and transport chief, Cllr Rowena Champion, said: "This pioneering project recycles heat that was simply being lost to the environment. We are cutting carbon emissions in a way that also reduces people's energy bills, helping us to help them at a time when the cost of living is soaring.
"Not only is this contributing to Islington's commitment to be a net zero carbon borough by 2030, but this initiative also helps to reduce fuel poverty and make Islington a fairer place, while offering our communities a sustainable, cheaper and greener future.
"I'm very proud of this exciting project, which promises to make a real difference to residents and the environment."
Up until now the district heating system has been powered by Bunhill 1, opened in 2012. Bunhill 1 has an engine that burns gas to produce electricity - the excess heat produced by this process is used to heat water, which is transported through pipes to communal boilers.
Excess energy produced by Bunhill 1 is sold into the national grid to cover its maintenance costs, and it has shaved 10 per cent off people's energy bills.
London's deputy mayor for Environment and Energy, Shirley Rodrigues, visited Bunhill 2 on Thursday last week to see the technology for herself and learn how it provides a blueprint for other sites on the Tube network, and for similar schemes that could use waste heat from other local sources, benefitting tens of thousands more Londoners.
On the new plant, London Underground's managing director, Andy Lord, said: "Capturing waste heat from Tube tunnels and using it to supply heating and hot water to thousands of local homes hasn't been done anywhere in the world before so this ground-breaking partnership with Islington Council is a really important step. Heat from the London Underground has the potential to be a significant low-carbon energy source and we are carrying out further research, as part of our energy and carbon strategy, to identify opportunities for similar projects across the Tube network."
TfL has undertaken a study on 56 ventilation shafts to assess the potential of each for exporting waste heat.
Detailed technical feasibility studies have been completed for the top six sites and TfL is developing its strategy to move these sites forward.
Key findings are expected to be shared later this year Islington Council says estimates homes connected to the district heating system will help reduce CO2 emissions by around 500 tonnes each year.
The town hall also says heating bills for council tenants connected to the network will be cut by 10 per cent compared to other communal heating systems, which themselves cost around half as much as standalone systems heating individual homes.
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