The share offer in Mighty River Power closed at 5pm on Friday.
The Government's sale of 49% of the power company has been hit by court challenges over water rights, uncertainty over the future of the Bluff aluminum smelter and plans by the Labour and Green parties to overhaul the energy sector.
Analysts say the opposition's proposals have spooked investors, particularly those considering investing for the first time.
More than 400,000 people pre-registered their interest in getting shares and investment banker Rob Cameron says if even a quarter of these invest, it is a very good result.
Radio New Zealand's economics correspondent said a successful float is crucial to the Government, which intends floating at least one more energy company by the end of this year.
Mighty River Power is due to be listed on the New Zealand Stock Exchange on 10 May.
