About 670,000 customers were without power late Monday in the city and suburban Westchester County.
"This will be one for the record books," said John Miksad, senior vice president for electric operations at ConEdison. "This will be the largest storm-related outage in our history."
New York's transit agency said water surged into two major commuter tunnels, the Queens Midtown and the Brooklyn-Battery, and it cut power to some subway tunnels in lower Manhattan after water flowed into the stations and onto the tracks.
The subway system was shut down Sunday night, and the stock markets never opened Monday and are likely to be closed Tuesday as well. Schools were closed and Broadway theaters were dark.
Image: This photo provided by Dylan Patrick shows flooding along the Westside Highway near the USS Intrepid as Sandy moves through the area Monday, Oct. 29, 2012 in New York. Much of New York was plunged into darkness Monday by a superstorm that overflowed the city's historic waterfront, flooded the financial district and subway tunnels and cut power to nearly a million people.