Cowen takes on the role after three years as director of consumer and business media relations for the recently privatised group.
As well as working on comms around the postal operator's privatisation, he worked with Eulogy on the company's headline-grabbing campaign to celebrate Team GB's 2012 Olympic gold medallists by painting a postbox gold in their home towns. This was one of the PR indsutry's favourite campaigns of the year.
Cowen, who steps into the job after Elliot Grady’s recent departure for BDO, told PRWeek that he felt it was time to move on.
He said: "After the postbox campaign and privatisation, both of which were exciting things to be involved in, I was looking for a new challenge.
"The energy sector is a very interesting one, with lots of scrutiny on it in terms of the public debate, so I really look forward to getting involved in that."
His arrival comes as the energy industry awaits the findings of the newly created Competition and Markets Authority, which is running a competition investigation into the sector.
British Gas director of comms George Eykyn called Cowan a "highly experienced comms professional, with a lot to offer British Gas."