Power company Exelon says its fourth quarter profit fell 18 percent, as demand for electricity in the U.S. remains soft in the weak economy.

Exelon made $581 million, or 88 cents per share, for the quarter ended Dec. 31 compared with profit of $707 million, or $1.07 per share, in the year-ago quarter. Revenue fell to $4.12 billion from $4.49 billion a year ago.

Exelon, one of the nation's largest power generators, says demand during the quarter continued to be weak at its utilities in the Chicago and Philadelphia areas. It says it also was hurt by outages at its nuclear power operations because of more scheduled refueling days.