South Australia's electricity distribution company has apologised to 60,000 customers it wrongly blacked out during last week's heatwave.
An investigation into the load shedding exercise, which resulted in 90,000 properties losing power for about half an hour, has revealed more power was shed from the network than necessary.
As power consumption soared to record levels, the Australian Energy Market Operator asked SA Power Networks to cut demand by 100 megawatts.
But instead an automated computer system shed three times as much.
SA Power Networks has apologised for the software error.
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"We have put in place steps to prevent a recurrence while continuing detailed technical investigations into why the load-shedding software did not operate correctly," the company said.
In its report into the load shedding, AEMO also said cutting electricity use was the only remaining viable option to avoid damage to the network after demand soared higher than expected and power from wind farms fell more rapidly than forecast.
The Climate Council said the market operator had let South Australia down in how it handled the energy supply issues.
"AEMO did not adequately protect South Australia," it said.
"Despite many days notice of the looming heatwave, AEMO did not ensure reserve supplies were operating in the event demand increased suddenly."
South Australian Energy Minister Tom Koutsantonis has also continued to criticise AEMO for not ensuring a gas power generator in Adelaide was fired up in time to cater for the extra demand.
"This report shows that South Australia reached its highest ever demand on Wednesday when the national operator decided to shed customers," he said.
"But it also shows we had enough local generation to meet that record demand but it wasn't turned on."
