The power was back on by 8:06 a.m. for all customers.
Three feeders were restarted remotely, restoring power to almost 4,000 customers within minutes, said Thelma Hatzis, a spokesperson for the company.
However, a crew had to be dispatched to two others, leaving 1,800 others still in the dark, she said.
The area affected is bordered by Hwy. 401 to the north, St. Clair Ave. E. to the south, Warden Ave. to the west and Bellamy Rd. N. to the east.
"We don't know what the cause is," she said.