That's what happened Tuesday, with Con Ed reduced power in Brooklyn and Manhattan. Power was also out in parts of Queens. All power though has been restored.
Record heat on Monday led to record usage, and Con Ed was forced to pull back the voltage to help avoid outages.
In Brooklyn, the utility reduced voltage by 8 percent. That affects about 123,000 customers in Greenpoint, Williamsburg, Fort Greene, Clinton Hill, Prospect Heights, Park Slope, Windsor Terrace and Bedford-Stuyvesant.
Con Ed also reduced voltage 8 percent on the Upper West Side to combat problems and try to prevent any outages there, affecting about 78,000 customers in the area bordered by 111th Street, Central Park West, 71st Street and the Hudson River.
Con Ed crews repaired the equipment, and the company is asking customers to turn off lights they are not using and to avoid using appliances like washers, dryers and other energy-intensive equipment.
Con Edison urges customers to call 1-800-75-CONED promptly if they are experiencing any service difficulties. Customers can also report power interruptions or service problems, as well as view service restoration information online at ConEd.com, and on their cell phones and PDAs.