The power went off about 12.30pm, with people on social media reporting outages as far afield as Hampden, Duntroon and Waitaki Bridge.
In a Facebook post at 3.15pm, Network Waitaki said it had managed to complete the restoration of the network following the "major Transpower outage" in Oamaru.
Network Waitaki said if there was still no power at your property, it may be a localised issue the company was not aware of.
"Please call our faults number on 0800 440 220 if you still have no power.
"We apologise for the inconvenience and thank you for your patience. It was a very busy day for our team dealing with this."
Transpower NZ said on its Facebook page that one circuit was out for maintenance and "unfortunately the second circuit tripped".
It did not yet know why this had happened.
