Progress Energy and Duke Energy cleared their final regulatory hurdle to merge the two companies, a move that would form the largest utility in the country.
In a 7-0 decision, the South Carolina Public Service Commission approved the agreement between the two utilities to join their operations for one year with a review at the end of that period.
Tom Williams, a Duke spokesman, said the company accepted the commission's terms and plans to close the merger deal this morning.
On Friday, the North Carolina Utilities Commission approved the deal.
The approvals end a regulatory process that began in January 2011, when the two North Carolina-based utilities announced they would merged their operations in a $26 billion deal.