Prime Minister John Key says shares in the state-owned assets put up for partial privatisation will be affordable for the average New Zealander.
Mr Key says the Government will try and price the shares so that the average investor can buy shares direct in their own name, and not just through their KiwiSaver account.
He says although some will be unable to afford to invest, he believes a price of $1000 for the smallest parcel would be affordable for a lot of New Zealander investors.
The Government is also justifying the amount of money it intends to spend on advertising the partial sale of state-owned assets saying investors need to have information about what is on offer.
The Mixed Ownership Model Bill passed in Parliament by 61 votes to 60 on Tuesday with the support of two of National's confidence and supply parties, ACT and United Future.
The legislation opens the door for the sale of up to 49% of shares in Genesis Energy, Meridian Energy, Mighty River Power and Solid Energy.
One of the first steps will be to launch an advertising campaign, aimed at enticing potential investors.
Future investors will be asked to register their interest in Mighty River Power, the first company to be partially sold, after which a price will be set.
The Government will be able to proceed with the partial sale after the company's end of year financial statements are issued on 30 June. Market conditions permitting, the share sale will take place before the end of September.
Opposition parties have criticised the Government for spending money on public relations, saying it lessens the value of the share float.
New Zealand First leader Winston Peters says direct costs of the asset sales, including an advertising campaign, will be up to $120 million.
Finance Minister Bill English says it's important to provide information about Mighty River Power and the benefits and risks of investing.
"It's important that people know about the company itself, which is not well known, and particularly because of previous investor experiences, such as with finance companies, people now understand they need to have a good grasp of what the assets are and what the risks are. "
Mr English says some decisions have yet to be made, including whether bonus shares will be offered to some investors.
Treaty hearing 'could affect asset value'
The Maori Council says a Waitangi Tribunal hearing to consider its claim over the water used by a number of electricity generators could affect the value of the assets.
The Tribunal considering the council's claim begins on 9 July.
Council co-chair Maanu Paul says the Government should not have passed the legislation allowing partial sale of state owned energy companies before the Tribunal made its finding.
Mr Paul says people buying power company shares need to consider that the value of their investment could decline if Maori are found to own the water and are able to attach a value to it.
Shares 'likely to stay in NZ'
International investors are unlikely to be interested in shares in state-owned assets, the head of Tower Investments says.
Chief executive Sam Stubbs told Morning Report he believes the vast majority of the shares will be owned by New Zealanders and by KiwiSaver and the National Superannuation fund.
He says most overseas investors would be interested in whether they could ultimately take over the company and this is extremely unlikely in New Zealand as the Government has made it clear it intends to retain 51% of the companies and therefore, control.