Aotearoa New Zealand's election result may not be known for weeks, with counting at the half-way mark showing a deadlocked race.

A narrow win for the conservative government, or Labour-led opposition, or even a dreaded hung parliament are all options still on the table.

What appears clear is that teal force Opportunity are heading for parliament, with 5.6 per cent of the vote.

The National party has also lost key personnel, with Finance Minister Nicola Willis and Defence Minister Paul Goldsmith all but conceding their seats.

The picture elsewhere is far more murky, with National and Labour swapping places as the biggest party in a tight count.

With 60 per cent of the count completed, Prime Minister Chris Luxon's centre-right National party led with 29.4 per cent.

In the second-straight Battle of the Chrises, Chris Hipkins' Labour was just behind on 29.3 per cent.

Those national voteshares are less important than the total number of seats each party and their coalition partners will win in the next parliament.

The electoral commission projects the government parties of National, ACT and NZ First will hold 67 seats.

Opposition parties Labour, the Greens and the Maori Party, when joined by Opportunity, reach 63 seats.

Those numbers have been moving around all night, dependent on both the national party vote and individual races.

ACT leader David Seymour, whose party is on a record high 10.9 per cent, said he didn't know whether he would be returning to government.

"It's going to take some time before it becomes clear," he said of the overall outcome.

"What I do know is it's a record result for ACT tonight and we are so happy."

The Greens have also claimed a record vote, with 13.7 per cent, while the Maori Party polled just 0.6 per cent but could yield five MPs after campaigning in electorates.

Those MPs, as well as six from teal force Opportunity, sitting on 5.7 per cent of the vote, will be critical if the left can claim a majority.

The result of the election has been in the balance for the entirety of the six-week campaign, which was dominated by cost of living issues.

On the early numbers, it appears National's vote will produce an overhang, which will be the other pivotal factor determining the government.

In New Zealand, voters get to make two votes: one for an electorate MP and one for a party.

The proportional representation system is meant to produce a parliament that reflects each party's share of the nationwide party vote.

However, if Kiwis vote for more electorate MPs from a particular party than their party vote would entitle them to, they get to keep the extra MPs in what is called an overhang.

Right-wing coalition parties ACT and NZ First have urged right-leaning voters to embrace strategic voting to maximise the overall share of MPs from the right.

The collapse of the National party's vote - from 38 per cent at the last election - while maintaining an edge in many electorates puts them on track for that overhang.

It's the factor that has ended Ms Willis' and Mr Goldsmith's careers, along with Speaker Gerry Brownlee.

"It is looking very unlikely I will be returned," Ms Willis said, saying a "process of renewal" was underway.