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.

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,

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