Built within 18 months and officially opened in South Australia on Tuesday, AGL Energy's first operational grid-scale battery covers an area the size of the Adelaide oval.
Energy and Mining Minister Tom Koutsantonis told AAP the Torrens Island project vindicated a decision to pioneer big battery technology for a secure electricity supply.
"That decision was at the time derided as little more than a tourist attraction, akin to the Big Banana or Big Pineapple, but it has set a template that is now emulated around the world," he said.
Scott Morrison, then treasurer, had mocked the state's first big battery - the world's first - that was built at Hornsdale.
More than 70 per cent of South Australia's electricity is supplied by renewables.
"We want this to grow as we reduce dependence on expensive gas and unreliable coal power," Mr Koutsantonis said.
Instead of turning off people's home solar energy systems when there is an excess of supply, a big battery can receive and store that cheap energy instead of wasting it.
"We can then supply energy after the sun goes down, potentially putting downward pressure on price," Mr Koutsantonis said.
Opening the 250-megawatt battery with the minister, CEO Damien Nicks said AGL was playing its part in Australia's energy transition.
"Importantly, this milestone demonstrates how we can make the most of our grid connections, land and people to redevelop our thermal generation sites into industrial energy hubs," he said.
The Torrens Island big battery can provide enough electricity to power 75,000 homes for one hour, with the option to extend the duration to four hours with a future expansion.
There are 218 battery cabinets housing more than 6000 battery modules.
It can respond to the requirements of the SA electricity grid in milliseconds by providing additional capacity and frequency control when gas plants can't do so.
Once the site of South Australia's largest power plant, the last units of the old gas generator are scheduled to close in mid-2026.
And while other states will have big batteries on the sites of former fossil fuel power stations, Torrens Island will use a mix of energy storage and new gas generation.
"On this very site in the past four years, we have announced the closure of a thermal power station, built a flexible peaking plant and commissioned the second largest battery in Australia," he said.
The "peaker" or rapid-start gas generator known as the Barker Inlet Power Station will operate alongside the big battery and can fire up within minutes to meet morning and evening demand.
"This is the transition in action," Mr Nicks said.
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