National Grid has said it expects to make about £70 million more than originally forecast from selling its Electricity System Operator (ESO) to the Government later than planned.

The FTSE 100 company sold the ESO, which manages the UK’s electricity supply, for £630 million last month.

The deal saw the ESO renamed as the National Electricity System Operator (Neso), and come back into public hands.

The extra £70 million in earnings came because the ESO sale, which was set in train by the previous Conservative government, happened later than initially forecast.

National Grid said on Thursday that it reflects “ownership and held for sale accounting treatment” up until September 30.

In May, the London-listed company said it would invest £31 billion on upgrading the electricity network across England, Scotland and Wales before the end of the decade.

The investment comes against a backdrop of fast-growing demands on Britain’s electricity network as the region transitions to renewable energy.

In 2023, research by the International Energy Agency found that engineers will need to roll out 600,000km of electric cabling before 2040 to help meet growing electricity demands.

National Grid said it will report its half-year results on November 7, where it expects core earnings per share to be higher in the second half of the financial year because of heightened demand for power over winter.

Meanwhile, Neso’s shift into public ownership in recent weeks has also seen its remit widen.

The organisation will advise Labour on how to achieve a clean power system by the end of the decade, with a report set to land on Energy Secretary Ed Miliband’s desk this autumn.

On Tuesday, Neso chief executive Fintan Slye told the PA news agency the policy will require the energy industry and the Government “to do things very differently, and to do things quicker, but it is nevertheless achievable”.

A primary challenge, Mr Slye said, will be to build things such as pylons, power lines and battery storage plants more quickly than before, which in turn will require the planning system to be “more streamlined”.

Officials will also need to cut Britain’s vast queue for green energy projects to get connected to the power grid, in which renewable energy projects face a waiting time of up to 14 years or more.

He said: “The ability to deliver infrastructure quickly on the ground is probably the biggest thing that we’re going to have to change.”