Progress and Duke Energy have been working on a $26 billion merger that would make it the largest electric utility in the country with 7.1 million customers in six states. It has come under Federal Energy Regulatory Commission (FERC) scrutiny, and the utilities have extended the termination date to comply with FERC’s stipulations.

The companies filed with the Securities and Exchange Commission to extend the termination date for the merger to July 8, 2012. The point of the termination period is to allow either company to exit the deal after that date, but they both have the option of agreeing to extend the deadline if they need more time.

However, Progress Energy spokesman Mike Hughes described the extension as a formality. The companies say the extension of the termination period does not change their estimate of when the merger will be completed. Both utilities maintain the March estimation.

The companies intended the merger to be complete by the end of 2011, but FERC expressed concerns about the state of competitive electrical service in the Carolinas. At press time, Duke and Progress intended to propose a plan that would protect competition under their merger.

FERC has rejected the deal twice over monopoly concerns.

Duke and Progress are considering selling several hundred megawatts of generating capacity to satisfy FERC and maintain the merger’s financial benefits to both companies’ customers.