E.ON, the German utility company and Powergen parent, approached TBWA\London in December after differences of opinion with RKCR/Y&R as to how the rebrand should be handled.
A spokeswoman from RKCR/Y&R said: "We were looking to retain and build on the 'positive energy' campaign, in view of the current political climate, where sustainable energy and environmental issues are seen as paramount."
E.ON plans to allocate £15 million for the rebrand, an increase in spend from £10 million last year. Neither E.ON nor TBWA would comment on the timings or media.
RKCR/Y&R has held the account since 2003. It has created a number of Powergen spots, including the ITV weather idents starring The Fast Show's Simon Day.