The Liberal Party has amped up its campaign against the South Australian Government over power — promising to appoint a "special investigator" on day one of any future Marshall Liberal government, to investigate Labor's early purchase of a power plant.

Premier Jay Weatherill and Energy Minister Tom Koutsantonis this morning exercised an option to purchase nine aero-derivative turbines, which it currently leases from US company APR Energy.

They are meant to provide up to 270 megawatts of backup generation should the state face the risk of blackouts over the next two summers.

The Government plans to take the nine turbines from their temporary diesel configuration at Elizabeth and Lonsdale and connect them at a permanent location, to become a gas-fired backup generator.

Under its contract with APR Energy, the Government was not required to exercise its purchase option until December 2018.

But the Premier said there was no good reason not to make a call before the election.

"This decision is an important decision to take now so we can put in place the planning arrangements, the commissioning arrangements, the selection of site and the preparation of ground works so that we can be in this power plant on the ground by the time of the next summer," Mr Weatherill said.

In a sign of just how politically charged the energy debate has become, the Premier and Energy Minister signed the contract alongside a stack of contracts relating to the privatisation of South Australia's electricity network under then-Liberal treasurer Rob Lucas 17 years ago.

SA Premier Jay Weatherill and Treasurer Tom Koutsantonis sign the contract. ( ABC News: Nick Harmsen )

"What was done today is undo some of those signatures that bear Rob Lucas's name ... We undo some of the damage that Rob Lucas did," Mr Koutsantonis told reporters.

The Government has refused to detail the precise costs of leasing and buying the turbines, declaring the figures are "commercial in confidence".

But the Premier said all elements of his $550 million Energy Plan remained within budget.

Liberals promise inquiry

Minutes before the contract was signed, deputy Liberal leader Vickie Chapman declared a Liberal government would appoint a "special investigator" to examine the decision to purchase the generators.

"If the Premier signs that contract today, on day one of a Marshall government we will commence an inquiry into this scandalous behaviour," Ms Chapman said.

"It's scandalous because the whole process of procurement is in secret."

Vickie Chapman has not specified the exact nature of the foreshadowed inquiry. ( ABC News: Nick Harmsen )

"To do this in a hurry, to save their own skin on the eve of an election makes it all the more despicable.

"It's a stinking rotten scandal and it is not an acceptable standard of government and it is unacceptable that our grandchildren are left with this legacy."

Ms Chapman was not specific on what form the investigation would take, but raised the prospect of a judicial inquiry with royal commission powers.

"Every person that's involved in this scandal will be called to account with a Marshall Liberal government," she said.

The Premier Jay Weatherill said any such inquiry would be politically motivated.

"If there is to be a judicial inquiry it should be into the privatisation of ETSA," he said.

Liberal Party won't rule out privatising power plant

Ms Chapman was less clear on whether a Marshall Liberal government would seek to privatise the taxpayer-owned power plant.

The Opposition's power plan, released last month, contemplated continuing the temporary lease of the gas turbines, but not proceeding with the permanent purchase of a power plant.

Instead, a Liberal government would contract backup generation from the private sector.

Ms Chapman repeatedly refused to rule out whether that meant a Liberal government would sell the taxpayer-owned turbines.

"The inquiry has to happen first. Obviously we'll be guided by that," she told reporters.

"It may not be enforceable, who knows."

SA generators to prevent blackouts in Victoria

The latest fight over the South Australian Government's generators came as the Australian Energy Market Operator confirmed they might be used to help prevent blackouts in Victoria this Summer.

AEMO's summer readiness plan confirms the operator has used emergency powers to procure 1,150 megawatts of back-up generation and demand-side measures to help alleviate the risk of blackouts across the national grid.

AEMO's believes it is 'well prepared' for the summer ahead. ( ABC News )

The powers — known as the Reliability and Emergency Reserve Trader (RERT) function — will see AEMO source 884 MW of demand side response, which can be called upon at relatively short notice.

The RERT will also include 266 MW of temporary diesel generation — including 170 megawatts from the South Australian Government's turbines.

The Energy Minister Tom Koutsantonis has confirmed the State Government will be paid if it is called upon by AEMO to turn its generators on.

"We will get paid in the RERT system, but not enough to recover costs and we're not attempting to make profit. We're just helping with the running costs of the generator," he said.

AEMO's report says it is "well prepared" for the summer ahead.

"In South Australia, the State Government's energy plan will be an important contributor to delivering new generation and energy storage for use in emergency situations during the coming summer, if extreme conditions occur," the report said.