Some Wangaratta homes were made to sleep through the first night of an extreme heat wave without power after an outage on Tuesday night.

An AusNet spokesperson said 4690 properties in the Wangaratta area lost power about 7:10pm.

Nearly 90 per cent of those affected had their power restored within 15 minutes, but some 560 homes had to wait until 5:15am the next morning for power to return.

Overnight temperatures hit a minimum of 18.1 degrees throughout the power outage.

“The cause of the fault is still under investigation, however damage to an underground cable was detected,” the AusNet spokesperson said.

“Further work will be carried out on the cable."

Planned outages, including in the Goorambat area, have been delayed due to the extreme heatwave passing through the state this week.

The AusNet spokesperson said crews were doing everything they could to shorten the duration of outages, which become more susceptible in extreme heat due to equipment failures, high demand and the impact of bushfires.

“We know it is difficult to be without power, especially in the heat, and apologise for the inconvenience,” they said.