The Berejiklian Government is set to negotiate a balance of power with five MPs from a range of political parties as three seats in the NSW Upper House remain in doubt, according to the ABC's election analyst Antony Green.

Key points: Antony Green said former federal senator David Leyonhjelm was a favourite to pick up a NSW Upper House seat

Antony Green said former federal senator David Leyonhjelm was a favourite to pick up a NSW Upper House seat But Green said that seat, along with two others, were still "in doubt"

But Green said that seat, along with two others, were still "in doubt" The Keep Sydney Open party's vote share has started declining as more regional NSW votes are counted

Almost two weeks after polls closed in the state election that saw Premier Gladys Berejiklian re-elected with a one-seat Lower House majority, the make-up of the Upper House — which Ms Berejiklian on Friday described as "challenging" — is still very much up in the air.

According to the ABC's election calculator, the Coalition is likely to pick up eight seats in the Upper House, bringing its total number to 17 including the nine continuing members from the 2015 election.

It had 20 Upper House members coming into the election.

The Coalition's total would come down to 16 in the event a Coalition-aligned Upper House president is elected.

Labor will get six Upper House MPs from last month's poll, bringing its total to 13 — up one seat from its total members before the election.

The Greens are likely to pick up two seats, which would bring its total to four members of the 42-member Upper House were it not for the resignation of Greens MP Justin Field.

Mr Field announced on Friday he was leaving the Greens to become an independent MP.

Antony Green said three Upper House seats are still in doubt ( ABC: Daniel Boud )

ABC election analyst Antony Green said assuming the Greens would not negotiate with the Berejiklian Government, the balance of power would rest with five Upper House MPs to get legislation over the magic 21-vote mark.

He said that would come down to negotiations with Mr Field, the Shooters Fishers and Farmers' two Upper House MPs, the Christian Democrats' Fred Nile, the Animal Justice party's Mark Pearson, One Nation's Mark Latham and, possibly, the Liberal Democrats' David Leyonhjelm.

But Green said three seats were still in doubt, including Mr Leyonhjelm's.

"I suspect Labor may have votes over the quota to pick up another seat," he said.

"David Leyonhjelm is tipped for one. The other seat will be decided between a second One Nation member, the Christian Democrats' Paul Green and an outside chance of [Tyson Koh of] Keep Sydney Open."

The Keep Sydney Open Party's candidates, including Upper House candidate and founder Tyson Koh ( Supplied )

Keep Sydney Open, a political party focused on Sydney's night-time economy and repealing the city's lockout laws, was tipped by some analysts earlier this week to sneak in with a seat in the Upper House.

However Green said current trends suggest the party's vote share has declined with further counting and would likely fall further, particularly as more Upper House votes came in from regional NSW.

Speaking on Friday morning, Ms Berejiklian said it would be a "challenging" Upper House.

"We have always known that," she said. "We had [that] in the last term of Government as well.

"What my Government's demonstrated is that you can still be a great, strong and stable government notwithstanding the configuration of the Upper House."

On Friday morning, 38 per cent of the vote was counted.

Mr Green said the final make-up of the Upper House would be known on April 12.