Because wind power generators operated only when there were significant winds, they were only about 30% efficient, Owens said. Wind also peaks in autumn and spring, rather than in summer and winter when power is most needed. So more conventional power stations were needed as back-up systems.

Therefore over-investing in wind power could unbalance South Australia’s power grid, Owens said.

The state has six licensed wind farms with a total capacity of 400MW that are expected to be operational in late 2005. Pacific Hydro is also considering building up too 200MW of wind power generators in south Australia

But across the Tasman, the chief executive of New Zealand's largest generation company argues that wind generators were a cheaper way of increasing power production than gas or coal generators.

"Of the research we have done, our wind program beats new coal and new gas-fired stations by a comfortable margin," Meridian Energy chief executive Keith Turner told the Rotary Club of Wellington.

"I know that there is enough wind and hydro power to provide secure supply for the next 15 years at a price well below coal or LNG," Turner said.

Turner committed Meridian to developing only renewable power such as wind farms and hydro stations and argued that when coupled with hydro generation wind power was reliable and clean.

"Variable? Yes over a day or a week, but actually highly predictable over a year,” he said.

“When the wind blows, we keep water in the lakes. When it doesn't blow, we generate from hydro. Perfect."

Meridian has built the biggest wind farm in Australasia – 90MW – at Te Apiti in the Manawatu Gorge, which can produce electricity profitably for less than 6 cents a kilowatt hour, he said. It was also seeking resource consents for a 70MW wind farm in Southland.

Meridian also owns Australia’s Southern Hydro.