"Z Energy has been a very good investment for Infratil and while an initial public offering will see us reducing our holding, we will still have a significant investment after the proposed IPO," Infratil chief executive Marko Bokoievski said in a statement.
The IPO returns are in addition to the $50 million special dividend to Infratil and the NZ Super Fund announced earlier this month.
The offer document forecasts operating earnings of $219 million in the 2014 financial year and $104 million in the first half of 2015, based on a historical cost measure, which is how it reports to the tax department.
Net profit is expected to be $115 million in 2014, and $50 million in the first half of 2015. The directors expect to declare a dividend of $88 million in the 2014 financial year, implying a gross dividend yield of 8.1 per cent to 9.4 per cent.
The bookbuild to set the price will be held on August 15 and 16, with a listing expected on August 19.
The offer is made up of a retail offer to broking firms and staff and an institutional offer. There won't be a public pool.