Benmore Dam hydro station in the Waitaki Valley (file picture). Photo: muha/123RF
Transpower says levels in hydro storage lakes are much lower than in previous years.
The power system operator says inflows into the lakes are now at the bottom of July norms since 1932.
In its regular weekly update it says the position is comparable to other dry years, including 1991, 1982 and 2001.
Storage levels were at about 60 percent of the norm for this time of year - with no significant inflows last week, Transpower said.
But electricity use tended to decline over the next few months of spring and into summer, it said.
Spot prices have risen because of the low hydro storage levels, and a higher than average proportion of thermal generation is being used, Transpower said.