At the same time, ministers have vowed to pump billions of pounds into green technologies such as carbon capture and green hydrogen production via the new state body GB Energy and a National Wealth Fund.
The ESO said it expected gas demand to be between 642 and 724 terawatt hours in 2030, at least a fifth higher than the previous minimum and at the top end of what was predicted just a year ago.
The minimum predicted demand for gas in 2035 has also shifted upwards, from 331 terawatt hours to at least 433 terawatt hours.
Today, the country consumes the annual equivalent of 872 terawatt hours in natural gas.
Even after power sources such as wind and solar are generating the lion’s share of electricity, it will still be necessary to keep some gas-fired capacity in reserve to ensure the lights stay on, the ESO added.
Joshua Buckland, a partner at Flint Global who was previously a civil servant in the Treasury and the energy department, warned that meeting the UK’s net zero targets would require “rethinking planning, how we do regulation, environmental approvals, as well as how we plan the energy system”.
He added: “I think that’s the question I’m maybe a little more concerned [about]: whether we are willing to carry through the bold, radical policy and political decisions that are going to be needed to deliver.
“Are we serious about getting infrastructure built in this country over the timeframe that is required?”
The ESO’s report did not give reasons for the higher expected gas demand.
But Kathryn Porter, an independent energy analyst, said two likely reasons were regulator Ofgem’s decision to block a series of new electricity interconnectors with Europe, which were previously part of the ESO’s calculations, as well as the expected closure of various nuclear power plants this decade.
Ms Porter added: “It means you will just not be able to meet demand by the end of this decade without more gas.”
The ESO’s latest predictions, made before the general election, do not take into account policies that Labour has pledged to enact in government, such as accelerating investment in green technologies and making the power grid net zero by 2030.
In the same report, published on Monday, the ESO says important decisions must be taken urgently to keep the UK on a viable path to net zero carbon emissions by 2050.
For example, it warns that between three to 18 terawatt hours of hydrogen storage is needed by 2035 – partly to burn when output from renewables is low. For 2050, the figure rises to between 19 and 49 terawatt hours.
