A fault on Transpower's network cut electricity to at least 4000 properties in Raetihi, Taihape, Ohakune, National Park and Ongarue just after 9am on Monday.
Transpower spokesman Geoff Wishart said power was expected to be restored by midday.
In the meantime, power is being backfed to properties in National Park and Ohakune, and a helicopter is looking for the source of the problem.
It originates from the line to Ongarue from Arapuni Hydroelectric Dam. The supply line from the south is down and being maintained, so there has been little back-up for consumers.
Transpower apologised for the outage and said it would post updates on its Facebook page.
