The minor party could gain two seats in Queensland, including Liberal-held Ryan and Labor-held Griffith, based on ABC projections on Saturday night. Postal and pre-poll votes are still to be counted.

Greens leader Adam Bandt won the first lower house seat for the minor party in 2010 representing Melbourne.

A parliamentary balance of power held by the Greens would preference stable, effective and progressive government, he said.

Former Labor leader Bill Shorten said affluent people voted Greens because they don't have to worry about their finances.

"Part of the challenge for Labor in the inner-city seats, and I have to contend with the Greens in my seat too, is very affluent people tend to vote Green because they don't have a worry in the world," he told the Nine Network.

Former Liberal foreign minister Julie Bishop agreed and called it a "luxury" to vote for the Greens.

But Mr Bandt said voters told him they were supporting the party for the first time this election not only because of climate action but because they didn't see many key policy differences between the government and the opposition.

He credited a people-powered campaign in Queensland and as polls started to close on Saturday night, Mr Bandt was confident the minor party would pick up spots in the Senate as well as some lower house, inner-city seats.

"We didn't go small target. We were very clear that there is a better and fairer way and that is a big part of the reason why we are seeing the results," he told ABC News.

If the Greens do hold the balance of power on the crossbench, they would approach the parliament with an open mind, Mr Bandt pledged.

"It's stable and effective and progressive government that would be our priority with action on climate and action on inequality," he said.

The Greens held the balance of power along with independents on the crossbench following a hung parliament at the 2010 election.

Australian Associated Press