Auckland should have a new fleet of battery-powered trains in two years, after the council approved the purchase.
The 17 new three-car trains will be able to run on either overhead electric lines, or large battery packs.
The trains will cost around $200 million.
The trains will be able to reach the southern town of Pukekohe which is beyond the existing electrified network, as well as meet rising patronage.
Auckland Transport said rail patronage had risen at around 20 percent a year, and had continued longer and more sharply than expected.
It said the annual target of 20 million rail trips should be reached this year, five and a half years earlier than expected.
The current 57 train fleet is on track to reach capacity by 2019.