A spokesman for Vector said crews onsite were unable to start work on the damaged transformer while the serious crash unit investigates.
"As a result, we're not able to confirm the number of customers impacted," spokesman Matthew Britton said.
"Our crew will stand by until we're able to access the site again and will continue to evaluate options for redirecting the flow of power to restore some customers if possible."
Pictures from the scene of the crash show a BMW car crashed into the transformer, where it came to a stop.
The back window and rear taillight of the car were broken and the fence beside the footpath and ground ripped up.
Fire crews on the scene after the car crashed into a transformer. Photo / Hayden Woodward
A police spokesperson said the driver sustained serious injuries and was transported to hospital by ambulance.
The passenger of the car, which side hit the transformer, reportedly suffered minor injuries.
Cordons have been put in place between Lyncroft St and Wickham Way on Buckland Rd and police expect the road to be closed for some time.
Auckland Transport said delays should be expected when driving through the area and advised motorists to avoid the crash site if possible.
Britton urged the public to stay safe on the roads and take extra caution around any electrical equipment which had been damaged.
"Network equipment should always be treated as live, and if they see them damaged or down following incidents like this," he said.
If anyone comes across damaged power equipment they are advised to keep clear and contact Vector on 0508 VECTOR.
BUCKLAND RD, MANGERE - ROAD CLOSED - 3:00PM Due to an earlier crash, Buckland Rd is CLOSED between Lyncroft St and Wickham Way. Expect delays and avoid the area if possible. ^TH pic.twitter.com/Z894lgKYfh
