Shares in Mighty River Power closed their first day of trading on the NZX at $2.62 - a 12-cent (4.8 per cent) premium to their issue price but down from their opening price of $2.73.
Trading was hectic when it kicked off at 12.30pm but activity slowed as the day progressed, brokers said.
By the close, about 70 million Mighty River shares had traded on the NZX.
Retail investors appeared to have been net buyers throughout the first day and there was a broad mix of domestic and offshore trading, market sources said.
Most of the offshore-based trading came from countries within the New Zealand time zone - Australia and Asia.
Europe and US investors are expected to be part of the mix when business resumes on Monday, one broking source said.
Light volume in Mighty River River shares was reported on the ASX, where the stock also debuted.
The shares started trading locally at $2.73 - a 23c or 9.2 per cent premium to their issue price.
Market expectations were for the stock to list at a premium because of the extent of unsatisfied demand from institutions.
The government raised $1.7 billion selling 686 million shares, or 49 per cent of the company, at $2.50 each to local and overseas investors.
New Zealand institutions were allocated 8.6 per cent of the shares on offer and overseas funds got 13.5 per cent, with both scaled back considerably.
