Orion says it aims to restore electricity to all customers in Canterbury by the end of the week.
About 1000 customers are still without power since the magnitude 7.1 earthquake that damaged an estimated 100,000 houses in the region at 4.35am on Saturday.
Orion says hundreds of contractors are working around the clock and are now trying to re-connect more isolated areas.
Chief executive Roger Sutton says the crews have made good progress since Saturday night when 20,000 customers were without power. But he says the network is in a fragile state.
Mr Sutton says Orion aims to restore power to all customers by the end of the week.