It was the country's biggest float since the NZ$1.12 billion listing of Contact Energy in May 1999.

Auckland-based Vector is controlled by the Auckland Consumer Energy Trust (AECT). It issued shares worth $NZ593 million ($A545.34 million) - representing 25% of the company - in a partial privatisation.

Based on Monday's prices, Vector has a market capitalisation of $NZ2.9 billion ($A2.67 billion), making it the fifth biggest company on the NZSX.

The capital raised will go towards funding last year's 66 % takeover of gas metering and distribution company NGC.

NGC will be fully merged into Vector and delisted from the stock exchange now that Vector has surpassed the 90% ownership level necessary for compulsory acquisition of all NGC shares.

Shares in NGC, which has acted as a proxy for Vector since the takeover was announced in early June, rose as high as $4.13 – an all time high - before closing up 21c at $4.06.

The Vector IPO was so popular that the institutional and primary market participant offers did not proceed and the beneficiary offer - for customers of the Auckland Energy Consumer Trust that owns Vector - was significantly over-subscribed.

NZX chief executive Mark Weldon welcomed the listing of Vector – the only remaining significant New Zealand-owned energy infrastructure company – saying its arrival added breadth and diversity to the market.

"It is extremely positive to see a company the size of Vector join the capital market,” Weldon said.

“It is positive for the company, the market and the country. The outstanding response to the offer shows there is strong investor appetite for quality companies in New Zealand."

Vector will make a preliminary full year profit announcement, including NGC results, on Friday.