Hawke's Bay is facing more power outages a week after thousands of people had their power switched off on one of the coldest nights in the year.
Transpower, which owns and operates New Zealand's national grid, said in a statement posted to social media on Monday morning due to an issue with "local generation" two power companies have been asked to reduce their electricity use in the area.
Unison and Eastland networks have been reduced and Transpower says it is working hard to get people in the region reconnected "as soon as possible".
It comes a week after Transpower was forced to shut off power to swathes of the North Island due to an insufficient amount of generation to meet the demand that came with one of the coldest nights in the year.
"Insufficient generation has been made available to meet demand and manage a secure system," it said last Monday evening.
"As a result, Transpower in our capacity as managers of the power system (the system operator) has asked the distribution companies to reduce load across the country.
"Different companies will do this in different ways."
Jacinda Ardern said on Tuesday there are questions to be answered about what happened.
"We cannot, hand on heart, say right now that all of the generation that could have come online did come online. That is a critical question. There may still be a case that this could have been prevented," she told reporters.
"We need to know as quickly as possible whether that was the case because it means we can target our solution. What happened wasn't good enough, even if it really was a peak on an extremely cold night, it is still not good enough that we weren't able to warm our homes."