Lines companies in Canterbury are working through the weekend to get power back to customers following Tuesday night's storm but say some may have to wait another four days to be reconnected.
Orion reconnected 3000 customers overnight, leaving 3000 still without power.
The company says more storm damage is being discovered as faults are fixed and hundreds of customers may now have to wait until Tuesday to be reconnected.
It is asking people having generators installed to have the work done by a registered electrician to prevent surges back through the network, which could electrocute engineers repairing the network.
In North Canterbury, Main Power says 1300 to 1400 households are still without electricity.
The company says it's confident only those in isolated areas will be without power by Monday.
In the lower North Island, Powerco says power is now restored to all its customers.
About 30,000 customers were cut off in the South Island and 10,000 in the North Island at the height of the storm.