The national grid operator said the restored power is not sufficient to power the whole of both regions.
Two main options are being explored to prevent Hawke's Bay and Gisborne being left without power, potentially for weeks.
A crucial substation has flooded on the outskirts of Napier, cutting off electricity to Hawkes Bay and Gisborne for "days to weeks".
Challenges in the energy sector mean it's time for a dedicated energy ministry.
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