When it comes to power outages, there is strength in numbers: The more of your neighbors who are also suffering from a lack of power, the sooner the electric utility will address your outage. An outage that affects only one individual customer is last in line.

As Peco's storm recovery efforts stretched into a third day following Friday's nor'easter, the utility was systematically restoring power to customers. Out of 630,000 customers who were affected by the storm, about 40,000 still had no power Monday evening. That was about 2,245 separate outages — or about 18 customers per outage.

Peco said about 1,000 mutual assistance workers from utilities as far away as Texas were working on its system Monday, reinforcing Peco's workforce of 2,600 employees, including back-office personnel. While racing to restore service by midweek, the utility has one eye out on a second nor'easter forecast to arrive on Wednesday, said Liz Williamson, a Peco spokeswoman.

>>MORE TO COME: Second nor'easter en route as region still recovers from last week's storm

After a storm hits, utilities follow a standard practice enshrined by state regulators across the nation and restore power first to critical public safety and health facilities: police stations, hospitals, nursing homes, and operations such as water-pumping stations, without which water taps would gradually begin to run dry.

Contract electrical workers from Illinois repairing a power line on Old Gulph Road in Bryn Mawr on Sunday.
MICHAEL BRYANT / Staff Photographer
Contract electrical workers from Illinois repairing a power line on Old Gulph Road in Bryn Mawr on Sunday.

The Pennsylvania Public Utility Commission, which closely monitors storm responses, also encourages electric utilities to work with county emergency management officials during storm events on critical infrastructure prioritization, said Nils Hagen-Frederiksen, the PUC's spokesman.

Then utilities prioritize outage repairs by the number of customers affected. The least-complicated repairs that affect the most customers get the highest priority.

Customers at the beginning of a circuit — those nearest substations — also move up the priority list because their service may affect customers farther downstream on the distribution system.

As the total numbers come down, each fix restores a progressively smaller number of customers. The utility may require as much time and expense to restore service to one or two customers at the end of a circuit as it did to repair a single fault that knocked out 1,000 customers.

Atlantic City Electric, which was not hit as hard as Pennsylvania utilities by Friday's storm, reported it had 1,184 customers out of power in 345 separate outages on Sunday. By Monday afternoon, ACE had reduced the number of dark customers to 176. But it still has 107 separate outages, or fewer than two customers per outage.

Peco's chief operating officer, Mike Innocenzo, said in an interview Sunday that he knows it is cold comfort to customers still without power that the utility was able to restore service to more than half a million customers in 48 hours. Some remote customers may not be restored until midweek, he said.

"We certainly understand the frustrations, and we get how important it is," he said. "Until we get the very last customer on, we're not done, and we continue to pull in resources and work around the clock until we get every last customer on."

Peco, which has 1.6 million customers in Philadelphia and five other counties, indicates on its online outage map that some customers could be without service through Thursday.

With modern smart-grid technology, utilities now can automatically determine which customers are not getting service, and sometimes can remotely divert power to affected customers from neighboring circuits and partially restore an outage.

Once utilities determine which customers will get repaired first, they try to communicate a realistic estimated restoration time to customers. They have learned from experience the pitfalls of failing to meet overestimated restoration times.

A risk that utilities also face with promising restoration times is that upon fixing a fault, they discover some remaining customers on the circuit still lack power because of a previously unknown fault — a "nested outage." A nested outage then becomes a new job that reenters the utility's repair queue, sometimes with a lower priority.

Elected officials often pressure utilities to fix the faults of their constituents first, and utilities employ vast teams of government affairs experts to maintain communications with local officials.

Regulators frown on any favoritism.

The PUC in 2014 fined PPL Electric Utilities $60,000 for diverting a repair crew during a storm to fix an outage in the neighborhood of the utility's vice president for distribution systems. The commission's investigators were alerted by a tipster, though it took a two-year battle by Pennsylvania media outlets to force the PUC to disclose who was the beneficiary of PPL's preferential treatment.