The Edison Electric Institute, an industry group, estimates 67,000 workers from utilities and other firms in several states worked to restore power, but they faced a huge volume of work. For example, New Jersey's biggest utility, Public Service Electric & Gas, had to cut down 41,000 trees, replace 2,500 poles and install 1,000 new transformers. At its peak, 77 percent of PSE&G'S 2.2 million customers lost power.Sandy also dumped 2-to-3 feet of snow in West Virginia, knocking power out to a quarter of that state's customers. And efforts to restore power along coastal properties were complicated by a storm surge that flooded dozens of substations on Long Island, in New York City and in New Jersey. For example, a storm surge and subsequent explosion at a substation on the East Side of Manhattan plunged the lower third of that borough into darkness. Equipment in all of those substations had to be cleaned or replaced before the substations could be re-energized. Only then could utilities see if the lines between each substation and the thousands of customers each one serves also had to be repaired. Utilities first fix problems that affect the largest number of customers, then work their way down to smaller problems affecting handfuls of customers. With Sandy and other big storms there are also thousands of customers who cannot get power because their homes are damaged and it is not possible or safe for the utility to restore power. This restoration approach is reasonable, experts say, but it leads to intense frustration when those last few in the dark see their neighbors back to normal. Customers are generally understanding for two days without power, utility officials say. Then they are not. Those last few homes and businesses, such as Kusack's firm, are often the hardest to restore; on many occasions, the days turn into weeks. After Con Edison restored power to nearly all of its customers 10 days after the storm, it said it was facing 3,600 restoration jobs in Westchester County that involved 11 or fewer customers each. LIPA said midday Thursday that 2,942 customers were still without power, not including those in flooded areas who cannot receive power until their own equipment is repaired and certified.