Moody's says the storm is credit negative for P&C insurers in the U.S. and is expected to adversely affect earnings “during a year of unprecedented catastrophe losses.”

Tree damage is expected to be substantial as the storm piled snow on leaf-covered trees. The weight of the snow snapped many limbs and huge branches, which produced damage to homes and cars from downed trees and limbs.

Debris removal and auto accidents add to the tally of damages.

There may also be “time-element” claims such as reimbursement for additional living expenses—such as hotel stays—for those displaced from their homes during the power outage, Moody's says.

While no damage estimates have yet to be released, losses are expected to be substantial and will add more pressure to 2011 earnings that have already suffered from a number of weather related events loss events this year, the rating agency adds.

By Wednesday last week, NU Online News Service reported a number of insurers were receiving a large number of claims. In addition, the Insurance Services Office's Verisk Analytic's Property Claim Services declared the event a catastrophe—meaning insured losses will exceed $25 million in Connecticut, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania. States of emergency were declared in each state.

Insurers with a large presence in the Northeast are most exposed to claims resulting from the storm, Moody's says.

According to SNL Financial, the top five personal-lines insurers (home and auto) in the most-affected states in 2010 were Allstate Insurance Group, State Farm Group, Berkshire Hathaway Insurance Group, Liberty Mutual Insurance Group and Travelers Group.