Prices at the North Island reference point of Haywards fell 50.7% to an average $69.21 per megawatt hour (MWh), while at the South Island reference point of Benmore prices were 54.4% lower at an average $72.06 per MWh.
A six-week power saving campaign will end this week as there are no longer any fears about winter power shortages, which were prompted by lakes falling to their lowest level since 1992.
"With a more positive outlook for the southern hydro lakes and a more encouraging rainfall outlook, the industry sees no need to extend the campaign," said Patrick Strange, head of the power industry group behind the campaign.
National inflows were 116% of average over the week to Tuesday, compared with 140% in the previous week.
In the South Island, where virtually all power is produced by hydro power stations, inflows were 99% of average from 145% the previous week, while North Island inflows were 136% of average from 133% a week ago.
Wholesale market operator M-Co said New Zealand's stored energy over the past seven days was steady at 68% of average.
About 60% of New Zealand's electricity comes from hydro power.
Over the past week, there were estimated savings of about 4.6% of national demand.
National demand fell 1.6% to 111,150MW.
