AGL announced the planned expansion today, saying two larger or four smaller gas turbine generators and a new gas storage facility would be built at the facility, about 15km north-west of Adelaide.

AGL chief executive Michael Fraser said the company hoped to formally lodge an expansion application next January, with construction to proceed in a further two years if approved.

SA Premier Mike Rann said the proposed expansion would provide the state with greater security of electricity supply, especially during summer peak usage times.

"This expansion not only provides the state with greater energy security but will also provide many hundreds of jobs for South Australians during the construction phase," Mr Rann said in a statement.