Public Service Enterprise Group Inc, the biggest utility in New Jersey, said superstorm Sandy had caused severe damage to its infrastructure and it expected its losses to be material.
PSEG, whose shared were down 2 percent in early trading, said the damage to its transmission and distribution systems had led to the worst outage in the company's history, with 1.5 million customers without power at the peak.
The company, which has 2.2 million electricity and 1.8 million gas customers, said it was still unable to estimate its total losses from the storm, which also damaged generating infrastructure in northern New Jersey and flooded a large number of substations along the Passaic, Raritan and Hudson rivers.
"The magnitude of the flooding in contiguous areas is unprecedented," the company said in a statement accompanying its third-quarter earningsreport.
Towns along the New Jersey shore took much of the brunt of Sandy, which barreled through the U.S. Northeast on Monday night, flooding homes, washing away boardwalks, rupturing gas mains and crippling power supplies.
PSEG said it was working to minimize the time that customers would be without electricity or gas service.
The company said on Wednesday that it would take seven to 10 days to restore full power. As of Wednesday, electricity had been restored to about 818,000 customers, while about 882,000 customers were still without power.
PSEG said on Thursday it intended to seek recovery from its insurers for some of the damages.
Exelon Corp, a power company that serves Illinois and Pennsylvania, played down the impact of Sandy on its operations, saying that as long as the weather was normal for the rest the year, its full-year adjusted operating earnings would be higher than its prior forecast.
PSEG said its net income rose 18 percent to $347 million, or 68 cents per share, in the third quarter from $294 million, or 58 cents per share, a year earlier.
PSEG's shares were trading at $31.33 on the New York Stock Exchange. Exelon shares were up about 1.75 percent at $36.41.
PSEG filed a petition with the New Jersey Board of Public Utilities on October 26 seeking authorization to defer recording some costs related to the restoration of its gas and electric distribution systems.