Transpower has put out a notice warning power companies that they may be unable to meet demand if there are any unexpected failures in the North Island between 7.30 and 9am Friday morning.
The Customer Advice Notice, posted on its website yesterday, is warning firms that there is only a small surplus of generated power within that timeframe.
NIWA says Thursday night was forecast to be one of the coldest overall nights of the winter nationwide.
Mercury general manager portfolio Phil Gibson spoke to Corin Dann.
