Meridian has released its December operating report, saying national storage had dipped from 98% of the historical average in early December to 91% by January 12 - the South Island down to 91% while the North Island increased to 107%.
The South Island's east coast has been hardest hit by lack of rain in recent weeks, prompting fire bans and water and irrigation restrictions, with no short-term relief forecast.
Storage from Meridian's Waitaki system at the end of December was 27% lower than at the same time a year ago, having for the month dropped from 99% of average to 91%.
Meridian, the country's largest hydro generator, said its Lake Pukaki storage was just below average, at 94%. Lakes Manapouri and Te Anau were in the middle of the normal range.
''We're comfortable with the current situation. As always, we are keeping a close eye on conditions,'' a spokesman told The New Zealand Herald.
Craigs Investment Partner broker Peter McIntyre said wholesale electricity pricing can be volatile, being largely driven by inflows and levels of hydro dams, and can remain very high for extended periods in dry conditions - significantly higher than the retail price.
Over the medium to long term, Craigs expected average retail prices to rise faster than inflation, boosting the profitability of the industry as a whole.
''However, the slow economic recovery has meant that electricity demand has not grown as fast as anticipated, and the market is still in oversupply,'' Mr McIntyre said.
Forsyth Barr broker Andrew Rooney said operationally, Meridian had been performing well and its data produced for December was good, ''capping a positive start to 2015''.
He said Meridian's December generation volumes were down 12.2%, due to hydro inflows, but noted that the comparative December 2013 volume had been very high.
Its retail sales volumes for the month were up 1% and its average contracted sale price up 2.3%.
Contact Energy's last update, at the end of November, had South Island storage at 109% of the mean historical average and the North Island at 104%.
Mighty River Power will release its latest operating figures shortly, as will Genesis.
Mighty River said while industry-wide national storage was 93% of average, storage at Lake Taupo, which feeds its Waikato River network of stations, was above average.
Mighty River general manager of hydro/wholesale Phil Gibson said the make-up of the partially listed company's portfolio, including its large geothermal base (about 40%) meant it had a high level of resilience and flexibility to mitigate dry conditions.
