Lines company Powerco says about 1500 customers mainly in south Taranaki remain without power and most isolated customers could be without electricity for at least another week.
Overhead lines were brought down and a large number of poles damaged in the region during a severe storm at the weekend.
Power was restored on Tuesday to most of Patea, but about 120 properties on the outskirts of the township are yet to be reconnected.
Powerco says spans of lines across large valleys and rivers have been brought down and trees which have fallen in their path will have to be cleared before sections of the network can be rebuilt.
Network operations manager Phil Marsh says major construction projects are needed in remote areas of Patea, Waverley and the Waitotara Valley.
The work could continue into next week and some customers are facing prolonged power cuts.