The utility’s customers, bracing for one of the hottest days in New York City’s history, were consuming considerably more electricity than they had on any morning before. At the rate they were plugging in and cranking up air conditioners, the previous peak of demand would not merely have been topped, it would have been torched.
That was a frightening prospect for the officials huddled in a makeshift command center at headquarters in Manhattan. They had prepared for an unprecedented draw on their network of underground cables and overhead wires, which spans the city and some suburbs to the north. But none of them knew just how far the system could be stretched without a major breakdown.
Then, at noon, the operator of New York State’s power grid rescued Con Ed by ordering many businesses and other large consumers of power to cut back. Managers of office and apartment buildings turned up their thermostats, dimmed lights and took some elevators out of service.
The New York Independent System Operator said those “demand response programs,” which provide incentives to commercial users for helping out in times of high demand, cover about 800 megawatts in New York City, on Long Island and in the Hudson Valley.
On Con Ed’s system alone, they may have saved 400 megawatts on Friday, said John Miksad, senior vice president for electric operations. He said city officials also pitched in by switching on backup generators at some facilities, including Gracie Mansion and two wastewater treatment plants. Those city properties did not go completely off the grid, but they sharply reduced the amount of power they drew from it, he said.
“We were going up at a rate of 1,000 megawatts an hour,” Mr. Miksad said, describing the spinning of the load meter projected on a floor-to-ceiling screen as “rocketing.” He said the total demand would have surpassed Con Ed’s projected peak for the day by 100 or 200 megawatts “if not for these programs.”
Even with them in effect, power consumption kept rising through the afternoon, briefly spiking above 13,200 megawatts. Officially, the new high is 13,189, which was the average load on Con Ed’s system between 3 and 4 p.m.
By then, the strain was showing: Con Ed reduced voltage in parts of all five boroughs and several towns in Westchester. It took that step, which keeps the lights and air conditioners on but with a little less hum, to try to head off equipment failures.
Meanwhile, the utility’s crews raced around the city repairing scattered problems that, at various times, left thousands of the company’s 3.2 million customers without power. Most of the failures were fixed within a few hours, though one feeder cable that failed near the Richmond Hill section of Queens was not expected to be back in service until Saturday morning.
Just before midnight on Friday, nearly 30,000 Con Ed customers in New York City and Westchester were without power. More than 25,000 of them were in New York City, primarily in Queens, the Bronx and Staten Island.
Saturday promised a combination of relief and added worry for the people charged with keeping the electricity flowing. Most commercial customers draw much less power after their employees take off for the weekend, but most of those workers are likely to spend much of Saturday hunkered in their homes in front of TV screens, air conditioners and fans.
“The residential areas tomorrow are going to be just as big a test as the other areas were today,” Mr. Miksad said.