PRWeek reported in September that the account was out to pitch towards the end of last year.
British Gas reappointed Blue Rubicon in 2012 as its retained comms agency, to manage corporate and consumer PR. The agency had first won the account in 2007.
George Eykyn, director of comms at British Gas, said: "We’re pleased to confirm that we’ve appointed Weber Shandwick as our retained PR agency, following a highly competitive tender process.
"Blue Rubicon has served British Gas superbly for eight years, and we’re extremely grateful for the agency’s expertise and partnership during this time."
Weber Shandwick's brief includes developing campaigns for the Government-mandated smart meter roll-out, and Hive, British Gas' connected home brand.
Rachel Friend, managing director, Weber Shandwick London, said: "It’s rare that a UK brief this exciting, touching so many people and in an industry as nuanced and significant as the energy sector comes along. To say we are honoured and thrilled to have been chosen would be an understatement.
"British Gas has a unique, incredible history and is a truly iconic British brand. We can’t wait to get started and help the brand on the exciting next stage of its journey."
The account will be led by Stuart Lambert, strategy and creative director in the consumer team at Weber Shandwick London, and Hollie Adamson who will be the client experience lead with overall operational responsibility for all campaigns.