The Red Consultancy had previously held the consumer PR account, while Target PR handled the brand's B2B activity and Leeds-based Mortimer Chadwick Grey handled part of its consumer work.
The Red Consultancy will now handle all aspects of the brand's PR activity.
The Red Consultancy head of consumer brands Ed Staples and head of corporate Paul Davies will lead the team and report into E.ON retail PR manager Nick Sandham.
'Now that E.ON is our singular customer facing brand following the rebrand of Powergen last year, this change will help us focus on the challenges ahead as we look to communicate to all our customers on a range of issues from price to the environment,' said Sandham.
The agency will work with B2B ambassador Ellen McArthur as part of its remit.