A disused quarry in Adelaide's northeast will be turned into a pumped hydro power plant to help cut energy prices.
Tilt Renewables will build a 300-megawatt plant at the Highbury quarry, with the site picked because of its existing reservoir and road infrastructure, the company's chief executive Deion Campbell says.
"Storage has always been a key component of an electricity system and pumped hydro allows renewable electricity to be stored and used when required," Mr Campbell said.
The plant will generate power by pumping water from a lower reservoir to an upper basin during periods of low energy prices, with the water released later to engage a turbine and produce electricity.
The company also announced on Wednesday plans for a $90 million solar farm and 21-megawatt battery near Snowtown in the state's mid-north.
The state government has pledged just over $7 million in grants from its Renewable Technology Fund.
Energy Minister Tom Koutsantonis said the project would bring more competition to the market, and critically, more storage.
"The best way to have cheaper power prices is more renewable energy, firmed up by storage -- storage is the key," he told reporters on Wednesday.
After a statewide blackout in 2016, the government has embarked on a bold renewable energy plan, including building the world's largest lithium-ion battery with the help of tech billionaire Elon Musk, and a solar thermal power plant at Port Augusta.