Transpower said a helicopter cropdusting on private rural land cut its transmission lines at about 10.25am this morning.
The pilot is safe, and was able to land and report the incident to Transpower.
"We will need to repair the lines before we can get power restored," a Transpower spokesperson told The New Zealand Herald.
"At this stage we estimate this will take 24-36 hours, but we will have a better view of when we can get power restored as work progresses."
Local provider Alpine Energy said it was "actively exploring options to restore power to some areas today".
More to come...