RALEIGH — Progress Energy reported weakening electricity sales for what was to be the Raleigh-based power company's last year of independent operation before a planned merger with Duke Energy in Charlotte.

The revenues and earnings released this morning are a prelude to conference calls with Wall Street analysts and investors who will undoubtedly seek updates on the status of the delayed $26 billion merger.

The two North Carolina electric utilities were expected to file their merger revisions as early as last month and warned then that the deal could be delayed by six months as the revisions make their way through complex regulatory reviews.

The failure of the two companies to get their $26 billion merger approved by regulators last year means that Progress and Duke will likely spend the first half of 2012 operating separately as they work out terms that are acceptable to state and federal regulators.

The merger would create the nation's largest electric utility, with 7.1 million customers in six states. Progress has 3.1 million customers in the Carolinas and Florida, and Duke also has unregulated energy operations in South America and in the western United States.

In 2011, Progress slipped by every key financial measure for the year and for the fourth quarter, with an unseasonably warm winter contributing to declining sales.

Progress reported this morning that its ongoing earnings per share fell 13 percent in the fourth quarter and nearly 3 percent for the year.

Fourth quarter earnings fell to $114 million this year, or 39 cents per share, from $133 million, or 45 cents per share last year.

Full year earnings fell to $871 million, or $2.95 per share, from $889 million, or $3.06 per share.

The company's revenue dropped 25 percent in the fourth quarter, to $1.7 billion. Revenue fell 12.6 percent for the year, to $8.9 billion.

Progress reported that fourth-quarter and full-year electricity sales were down significantly, both in terms of revenues generated and kilowatt hours sold.

In the fourth quarter, electricity sales were down 11.1 percent in the Carolinas and 36.6 percent in Florida. For the entire year, electricity sales were down by 8 percent in the Carolinas and 16.8 percent in Florida.

The electricity sales declined despite the fact that Progress gained 6,000 customers in the Carolinas and 8,000 in Florida last year.