Centrica publishes the details of its split from British Gas at the end of this week, when it is expected to announce Sir Michael's appointment.
Shareholders will vote on Centrica's proposals at an egm on 12 February, and the shares are due to start trading five days later.
Sir Michael's expertise in marketing and brands, as well as his wide international experience, will add credibility to Centrica.
He joined British Gas as a non-executive director two years ago, and was given a similar post at Centrica last month.
He will be a non-executive chairman, leaving most of the decision making to Roy Gardner, chief executive. Richard Giordano will withdraw from Centrica and remain chairman of British Gas, the production and pipeline business.
Sir Michael, 62, joined Unilever in 1957 and worked his way up to become chairman four years ago. He retired from Unilever last September.
He helped to change the perception of Unilever in the City from an Anglo- Dutch company based on products like toothpaste and shampoo to a truly global business with prestige brands. For instance, he played a leading role in the acquisition of Elizabeth Arden and Calvin Klein in the late 1980s.
This brand awareness will be useful to Centrica, which faces stiff competition in domestic gas supply as well as the challenge of expansion overseas and into electricity.
Sir Michael is a chairman of the trustees of the Globe Theatre, the recreated Shakespearean theatre in London. He is also a keen singer and opera buff, often singing with the Bach Choir.
A spokesman for Centrica refused to comment on the appointment last night.