Power was fully restored at Grand Central Terminal on Tuesday morning following a power outage on Monday, the MTA said.

The busy terminal was plunged into darkness when a 6-inch water pipe burst just before 9:30 a.m., flooding a transformer house that feeds power to the station, MTA spokesman Aaron Donovan said. That led to 18 inches of water flooding the vault, knocking out power to the terminal and all 100 retail spots in the midtown station.

Train service continued, but all MetroNorth trains were running on upper-level tracks. The reduced holiday schedule allowed service to remain uninterrupted.

“It’s a weekend holiday schedule so we have no capacity issues,” Donovan said. “It would have been a problem if it happened during rush hour.”

Passengers were able to buy tickets using cash at teller windows. An announcement was made that they could purchase on board without paying any additional fees.

Loreta Carrero, 44, works as the florist manager of the Eli Zabar’s store in Grand Central. She was arranging flowers when the lights went out.

“We just all turned around and we immediately lost power, just like that,” she said, hanging around outside the market hours later. “You get a little nervous. It was dark. It was a little spooky.”

Likewise, Lakeisha Banks, 41, was plunged into darkness when she emerged from the subway on her way home to Waterbury, Connecticut.

“I’m a little nervous,” said Banks, who had been visiting family in Brooklyn with her 20-month-old daughter, Brielle. “I just came off the train and it was just black.”

But Banks was confident the issue would be worked out. Now, she had to focus on where to find a cup of coffee.

“As long as it doesn’t affect the trains, then I’m OK,” she said. “It’s not that bad because everyone is still moving around.”

But not everyone disliked the dark. Manny Lupian, 38, was waiting for friends inside the main terminal on Monday, happy that the lights were out.

“I love it,” said Lupian, who was visiting from Milwaukee and used to live in New York. “The architecture of the building actually comes out. You can kind of enjoy what Grand Central actually looks like.”