Mighty River Power suffered its lowest first-quarter hydro generation since the company was formed in 1999, down by more than a third in the three months to the end of September.
Commercial sales volumes fell 8 per cent for the period.
But chief executive Doug Heffernan said the company remained on track to achieve prospectus profit forecasts, despite the lower generation.
Hydro production from its nine power stations on the Waikato River was down 34 per cent in the September quarter. The lack of water in the Waikato River was partly offset by the extra geothermal production from its new Ngatamariki power station, which accounted for almost half the company's generation in the September quarter.
Its overall generation was down 18 per cent to 1621 gigawatt hours, the company said in its latest quarterly operational update. The report did not include any financial results for the period.
However, by the end of the quarter, Lake Taupo water storage was back at more than 100 per cent of its historical average, after heavy rain in September.
Heffernan said there was no clear connection between how the company was performing operationally and how its shares were trading, at $2.20 yesterday, still well below their original issue price earlier in the year.
"All we can do is focus on delivering the results we said we would in the IPO [initial public offering]," he said yesterday.
The company had beaten its earlier forecasts for the 12 months to June this year and confirmed it was on track for forecast operating profit for next financial year, despite weak hydro conditions in the first quarter.
Despite the fall in hydro generation, it got a better return for the power it did produce and was able to buy "smartly" in the wholesale market.
"We are trying to make sure that we hit those [prospectus] targets, come hell or high water," he said.
Electricity sales to its customers were down 5 per cent, reflecting lower national demand and a fall in commercial sales volumes, down 8 per cent, the company said in its September quarter report.
National demand was about 2 per cent lower than the same period last winter, with sunnier weather than last year reducing household electricity demand.
But Heffernan said the company was resilient to soft demand because it was mainly a renewable power company, relying on cheaper hydro and geothermal generation, while it was thermal-fired generation that would face greater pressures. "We will continue to do well, even if demand is weak."
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