About 500 houses in the Christchurch suburb of New Brighton lost power for about an hour on Tuesday.
There was no electricity between 6.30am and 7.30am due to a cable fault between two sub-stations.
Lines company Orion says the network is fragile following the damaging 22 February earthquake.
It says customers should be prepared for further disruption, especially as demand for electricity increases as the weather becomes colder.
