NEW YORK - Power company Exelon Corp posted an 8 percent increase in third-quarter profit, but its revenue fell far short of Wall Street expectations and it dropped its forecast to the bottom end of its previous range.

Utilities across the United States have seen revenue slump as the weak economy has dragged down electricity usage, particularly among commercial and industrial customers.

Net profit rose to $757 million, or $1.14 per share, from $700 million, or $1.06 per share, in the year-ago quarter.

Excluding the value of derivatives, regulatory settlements and other one-time items, earnings of 96 cents per share were in line with analysts' average forecast, according to Thomson Reuters I/B/E/S.

But revenue on an adjusted basis fell 17 percent to $4.36 billion, well below analysts' average forecast of $5.36 billion.

Exelon, which failed in a bid earlier this year to buy NRG Energy Inc, owns the ComEd utility in northern Illinois and PECO in southeastern Pennsylvania.

The company said it now expects full-year earnings per share between $4.00 and $4.10, the low end of its previous range of $4.00 to $4.30 per share. (Reporting by Matt Daily, editing by Gerald E. McCormick)