The government says it is open to trying new ways to increase voter turnout after the number of people casting their vote in local body elections fell to under 40 per cent.

Preliminary results reveal 39.5 per cent voted in Saturday's postal ballot, down almost 2 per cent from three years ago.

Organisers had been hoping for a turnout above 50 per cent.

Local Government Minister Peseta Sam Lotu-Iiga says the government is keen to look at initiatives to boost the numbers casting their ballot but cautions online voting may not be the solution.

"More work needs to be done to address concerns around security and vote integrity before a trial can take place. It is also important to note that international evidence suggests online voting has not led to a significant increased turnout in areas where it has been introduced," he said.

In Auckland, just 36.5 per cent voted where Phil Goff was elected new mayor, 37.2 per cent re-elected Lianne Dalziel in Christcurch while in Wellington, where there was a tight race to replace Celia Wade-Brown, the turnout rose by 0.6 per cent to 42.1 per cent as Justin Lester took the mayoral chains.

The Wellington result gives the capital its first Labour leader in 30 years and means all three of the country's biggest cities have Labour mayors.

"This has been a good night for the Labour Party," said president, Nigel Haworth.

Mr Lotu-Iiga said he was looking to building strong relationships with all those elected.

The closest result of the night was in Hamilton where Andrew King holds a 14-vote lead over Paula Southgate in the race to succeed Julie Hardaker.

Final results will be announced on Thursday, but there is a possibility of a recount if the vote remains close.

Elsewhere, Hastings mayor Lawrence Yule has been returned to office, while in Rotorua ex-Labour cabinet minister Steve Chadwick overcame opposition to a Te Arawa partnership to comfortably retain the mayoralty.

Tim Shadbolt has won an eighth term as mayor of Invercargill and Gisborne's Meng Foon has won a sixth term while Greg Brownless has been elected as the new mayor of Tauranga, beating 10 candidates to replace Stuart Crosby.

Tim Cadogan has unseated Tony Lepper to become Central Otago's new mayor, Kapiti Coast mayor Ross Church was dethroned by K Gurunathan and Horowhenua looks likely to have a new leader with councillor Michael Feyen holding a healthy lead over mayor Brendan Duffy.