North Carolina-based utility companies Duke Energy and Progress Energy have completed their merger Monday, forming the new largest utility company in the US, Duke announced Tuesday. The transaction was valued at US$32bn, based on Duke’s stock and including Progress’ debt.

Contrary to previous announcements, Jim Rogers, CEO of Duke, will continue to lead the combined company as chief executive. When the companies first announced their merger plans in January 2011, they said Bill Johnson, then CEO of Progress, would become the combined company’s CEO.

On Wednesday, however, Duke announced that Johnson would instead leave the company altogether by “mutual agreement” without providing an explanation. Ann Maynard Gray, lead director of Duke’s board, told the Washington Post the company would not address any questions about the decision.

Commenting on Johnson’s departure in a statement, Gray said, “Bill Johnson has been instrumental in helping us close the merger with Progress Energy, and we wish him well in his future endeavors.”

Date of the merger’s completion was also different from what was originally expected. In August, when Duke shareholders had approved the merger, the company said it expected to close the deal by the end of 2011.

It received final approvals from North and South Carolina utility regulators this and last weeks respectively, according to news reports.

Duke said the combined company’s market capitalization was $49bn and its 2011 operating revenue was $23.4bn. The new Duke owns 58,200MW of generation capacity in the US, serving electricity to customers in North Carolina, South Carolina, Indiana, Ohio, Kentucky and Florida.

In Ohio and Kentucky it is also serving gas.

Duke also operates and manages generation facilities in Latin America and has a stake in Saudi Arabia’s National Methanol Company.