Private prison firm Serco expects revenue of close to $30 million a year once the new Wiri prison in South Auckland is operating.
Serco last week signed a contract for the 960-bed men's prison as part of the National-led Government's first public-private partnership.
The prison will be designed, built and run by a consortium comprising Fletcher Building, Serco and Spotless Facility Services.
In a stock exchange announcement in Britain, Serco said it plans to make about $4 million in revenue a year before the jail opens in mid-2015 and some $30 million a year after that date.
Serco chief executive Christopher Hyman says the 25-year contract is an exceptional opportunity to deliver innovative and cost-effective services.
The contract is expected to be tabled in Parliament within the coming month.