Power was cut to 5000 homes and the international airport in Christchurch this morning.
Lines company Orion said the outage happened 9.30am at the Waimakariri Substation and the cause was still being investigated.
A spokesperson said electricity went out at Christchurch International Airport and homes in Belfast, Burnside, Harewood and surrounding areas.
An airport spokesperson said no international flights were delayed as generators kicked in when the outage occurred but domestic flights were held up.
The spokesperson said Orion's chief executive made contact with the airport and updated it on the outage.
Orion had to re-route power from other substations to restore supplies at 10.30am.
The spokesperson said the company was hoping to switch back to the Waimakariri Substation today and customers would not be affected or notice when the change took place.