Philip O’Brien, a spokesman for Con Edison, the city’s power utility, said that peak megawatt usage on Saturday in New York City and the nearby suburban county of Westchester was about 10,300, less than this month’s high of 11,500 megawatts, set on Wednesday. That peak itself was lower than in recent years, with the record being about 13,300 megawatts, set in July 2013.

That decline in usage over time is partly the product of more energy-efficient appliances, he said. Out of more than 3.5 million customers, only 27 were out of service late Saturday, a lower number than would be expected “after what we’ve been through this week,” he said.

“It indicates that the system has been fortified and it’s holding up,” Mr. O’Brien said, adding, “We’re hopeful that our good performance can continue into tomorrow.”

To protect the power grid, New York City officials asked residents to use less energy. Some suggestions included turning up the air-conditioner to 78 degrees and unplugging appliances like televisions and computers.

“You can hit the beach or head to the pool to keep cool, too!” the city said on Twitter (though not Rockaway Beach, which was closed on Saturday after shark sightings).