The storm that crippled South Australia's electricity system could also force OZ Mineral's to miss its full-year gold production guidance.
The company said on Monday that electricity transmission to its Prominent Hill mine is expected to be progressively restored over the next seven to 10 days, but warned full restoration of power was outside its control.
Gold production at the site is now expected to be at or below the lower end of its guidance of 125,000 to 135,000 ounces.
Copper production is will remain within guidance despite last week's storm, which left the entire state in darkness.
The site's open cut mine was not affected by the storm, but the below ground operation has only been able to resume in a limited capacity.
The company's processing plant remains on standby and has had maintenance programs brought forward.
