British Gas owner Centrica has signed a 10-year deal worth more than 20 billion pounds ($27.07 billion) with Norway's Equinor to secure gas supplies starting in 2025, both companies said on Thursday.

The agreement starting October and covering the next decade would meet around 10% of the country’s annual gas demand.

Equinor ASA EQNR, the Norwegian energy giant, and Centrica plc, owner of British Gas, have inked a £20 billion gas supply agreement for 10 years starting Oct. 1, 2025. Under the terms of the deal, Equinor will supply 55 terawatt-hours (TWh) of natural gas annually,