Powergen is to take on the name of its German parent company.
The Coventry-based energy group, which runs power stations and sells gas and electricity across the UK, said it would be known as E.ON UK from 5 July.
But the firm said its consumer retailing operation, which serves six million domestic and small business customers, will keep the Powergen name.
The company said next month's change would be a major step towards a single group identity.
The company's distribution arm, which supplies electricity to nearly five million people across the Midlands, and includes the former Midlands Electricity and East Midlands Electricity distribution operations, is now known as Central Networks.
The firm announced the creation of Central Networks in February with the loss of about 600 jobs.
The latest change means all the group's power station and wind farm operations and its industrial and commercial retail arm will be re-badged as E.ON.
Chief executive Paul Golby said: "With our parent company having already invested £12bn in Powergen, and shown a long term commitment to both us and the country, this move marks the next stage in our development."
The group has 10 oil, gas and coal-fired power stations in north London, Nottinghamshire, Kent, Wales, Shropshire, Northamptonshire and Lincolnshire.
It also has stakes in 20 wind farms and 16 combined heat and power plants located between Kent and Cumbria.
Powergen became part of German utility E.ON in 2002.