Defeated premier Jay Weatherill says he will resign as Labor leader after losing this weekend's election to the Liberals, while Steven Marshall says he will start getting the state "back on track".

Key points: Jay Weatherill says a new leader will be decided soon

Jay Weatherill says a new leader will be decided soon He says he has "zero ambition" to join the Federal Parliament

He says he has "zero ambition" to join the Federal Parliament Steven Marshall says getting the state "back on track" will be his focus

Mr Weatherill visited Government House late on Sunday morning to officially resign as premier, where he told reporters he planned to see out his term in State Parliament.

"I'm looking forward to being the state member for Cheltenham. It's a fascinating seat, it really is, and I'm really looking forward to going around and thanking everybody that supported me over the past 16 years," he said.

"I've been in an unusual position where I'm doing it a bit back-to-front. I was a minister before I really was a serious backbencher and I think that they need the attention of their local member of Parliament.

"I'm proud of what we've done locally, but I'm really looking forward to being a good local member of Parliament."

Asked if he might seek a future role with a national profile, he responded: "Absolutely not. I can say that with great passion I have zero ambitions to go into Federal Parliament".

Meanwhile, the SA premier-elect Mr Marshall and senior colleagues Vickie Chapman and Rob Lucas are to be sworn in by the Governor on Monday, with the rest of the Liberal team to be sworn in later in the week.

Sorry, this video has expired SA Premier-elect optimistic about his state's future.

Mr Marshall said there might be some minor tweaking of portfolios as his shadow team moves into their roles in government.

He told reporters in Adelaide he was looking forward to implementing the Liberals' plans for the state.

"Now it is our opportunity to get this state moving again. I'm absolutely delighted with the result last night," he said.

"I'm also delighted that we get so many new people into the Liberal line-up. In fact, I think it is now 11 new people into our team of about 33 people."

'We'll get the state back on track'

The Liberal victory ends 16 years of Labor government, and Prime Minister Malcolm Turnbull offered his congratulations to Mr Marshall.

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The incoming premier said job creation would be a focus.

"We will lower people's taxes, lower the cost of living, create more jobs in this state, get this state back on track," he said.

Asked if he would reward MP Vincent Tarzia — shadow cabinet secretary in the Liberal Opposition — for retaining the eastern suburbs seat of Hartley in the face of a challenge from ex-senator Nick Xenophon, Mr Marshall did not make any promises.

"I'm extraordinarily grateful to every person in the team. Every person honestly had their role," he said.

"I said this before, it is a little bit like a football team — you can't all be the centre-half-forward, you can't all kick the goals.

"Everybody had to play their part, and certainly Vincent Tarzia did a great job."

Labor will now start discussions on replacing Mr Weatherill in the leadership, and the outgoing premier said it had plenty of options.

"The Labor Party's got plenty of fantastic choices of leader. I won't be one of them but ... we'll have a good solid new team to take forward," Mr Weatherill said.

"We've really got some great new talent coming into the Parliament … so we've got to make room for them as well."

Jay Weatherill leaves Government House after resigning as SA Premier. ( ABC News: Alina Eacott )

SA Labor senator and right-faction powerbroker, Don Farrell, said "stable leadership" was important for the party.

When asked whether the next state leader should get two shots at an election, he told the ABC: "I'd be pretty surprised if the party weren't prepared to give that to our next leader."

Federal Labor leader Bill Shorten praised Mr Weatherill's leadership of the state, and his campaigning efforts despite Labor not achieving a fifth consecutive term.

"It was a very big ask after 16 years to get re-elected for another four years and I think he came very close," he said.

"I think he leaves South Australia better than when he found it and I think that South Australian Labor over the past 16 years have left it better than before they got elected."

Array of Upper House parties a challenge

The Liberal Party is projected to secure 24 seats in the House of Assembly, enough to govern with a majority in the Lower House — but Mr Marshall's legislative agenda might face challenges in the Upper House.

Labor looks set to keep three of the 11 places that were up for re-election in the Legislative Council, with the Liberals retaining four, SA Best gaining two and the Greens winning one.

Sorry, this video has expired Antony Green breaks down the SA election.

The other seat is expected to be claimed either by Labor or the Australian Conservatives.

Overall, voting across SA achieved a swing to Labor, but a redrawing of electoral boundaries delivered four more seats to the Liberals than in 2014.

Both major parties lost first preference votes to SA Best, which gained close to 14 per cent of the overall vote, but Nick Xenophon's SA Best party is predicted to miss out on any Lower House seats.

The outcome is a blow for Mr Xenophon, who quit federal politics to seek a return to the SA Parliament, where he previously served in the Legislative Council.

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Liberal senator Simon Birmingham tweeted details on Sunday of a new drink on the menu of a city cafe — The Marshall 2.0, a blend of banana, pineapple, spinach and passionfruit pulp.