Shoppers in Orchard Central were plunged into darkness on Saturday afternoon, as water seepage from a heavy downpour caused a blackout.
Many shops were forced to close early, losing business on an otherwise busy weekend in the run-up to the festive season.
The power outage at around 2pm affected about 50 shops in the mall's east wing.
Power was restored in some shops, as well as the lifts, within a couple of hours, but resumed fully for all the shops only around 1.30am yesterday.
Fusion restaurant Kilo was forced to cancel its dinner shift, taking in just under $2,000 on a Saturday, when it would usually see at least $5,000.
Manager Paolo Castillo said: "Some of the guests were upset, but we could only apologise and say it was beyond our control."
The refrigerators in Kilo's kitchen also stopped working.Staff returned the next morning to discover that many expensive, perishable ingredients, such as salmon and octopus, had gone bad and had to be thrown out.
Fashion retailer In Club had to close four hours early, at 6pm. Manager Jo Wan, 46, said: "The customers couldn't see anything. How were we going to get them to stay and browse?
"Losing one Saturday afternoon's business really costs us, especially while we're having our Christmas sale. There may be no customers, but we still have to pay rent and our staff still need to draw a salary."
Yesterday, business had returned to normal for most of the mall, although some escalators and the lighting on the facade of the building were still affected.
Mr Eric Tong, assistant director of retail business at Far East Organization, confirmed that water seepage during the heavy downpour caused the blackout.
He said: "We are now working towards fully restoring the power and investigating the source of water seepage.
"We regret the inconvenience caused to our tenants and shoppers, and will provide assistance and support where required."
At multi-label clothing chain The Editor's Market, however, the blackout failed to dampen spirits at a $15 storewide clearance sale.
Sales assistant Amanda Teo, 22, said: "We have big windows, so there was still some light. People would try on clothes in the dressing rooms, then walk outside to look at themselves in the mirrors.
"The power came back by 5pm and we closed at 10pm as usual."