Hydro One says two transformers caught fire at its Richview Transformer Station in the city's west-end Friday afternoon.
The four-alarm fire pushed thick plumes of black smoke in the air and forced the closure of Highway 401 near Pearson Airport for nearly one hour.
At one point, hundreds of people were lined up in their vehicles during the afternoon drive home.
Hydro One confirmed there were no injuries or health and safety issues reported as a result of the fire.
Toronto Hydro worked fast to get the power supply back to customers after the fire broke out. Within one hour, the electricity was fully restored.
Firefighters and emergency services remained on-site hours after the fire was under control. The cause has not yet been determined.
Peel police say that the fire did affect Pearson Airport, but backup generators kicked in and helped the airline service run as per usual.
With files from The Canadian Press