EDF Energy has snapped up a 10-year contract with Network Rail to supply electricity to the growing electrified rail network.
Under the contract, EDF Energy will supply around 3.2 terawatt-hours (TWh) of electricity a year to the network, which carries around 3m passengers a year.
At present only 40 per cent of the rail network is electrified, but by 2020 it is set to rise to 54 per cent.
Network Rail chief executive David Higgins said today: "Thanks to a firm commitment from government to invest in electrification schemes across the country, we are transforming the railway and providing Britain with a sustainable, world-class transport system that is fit for the future.
"This innovative contract for low-carbon energy will provide excellent value to the rail industry and means we are not only providing a greener railway, but also a better value railway for Britain."