Auckland railway electrification

Auckland railway electrification occurred in phases as part of investment in a new infrastructure for Auckland's urban railway network. Electrification of the network had been proposed for several decades, with work starting in the late 2000s after funds were approved from a combination of regional (Auckland Regional Council, later Auckland Council) and central government (NZ Transport Agency) budgets.

The contract for the electrification infrastructure was awarded on 14 January 2010 to an Australian and New Zealand consortium, while the contract for 57 trains was awarded on 6 October 2011 to Spanish manufacturer CAF. The first public electric service was on 28 April 2014 on the Onehunga Line. Since July 2015, all services have been electric with the exception of Papakura to Pukekohe, which runs a diesel shuttle service, and Swanson to Waitakere, which runs a bus shuttle service. Electrification from Papakura to Pukekohe has been proposed to the council, but is not in any immediate plans as the cost would be too high.

All four suburban lines between Swanson in the west and Papakura in the south are electrified at 25 kV AC, the same voltage as the North Island Main Trunk between Te Rapa and Palmerston North. In contrast, the Wellington suburban network (electrified 1938–55) uses 1500V DC.

About 3,500 masts were installed as part of the project. The Onehunga Line was the first line to be commissioned.

The system is supplied by two connections to Transpower's 220 kV national grid, one at Mighty River Power's Southdown Power Station and the other at Transpower's Penrose substation. Both connections are duplicated (Penrose has limited duplication due to having only one 220/25 kV transformer), and one connection can supply the entire network if the other one fails, creating a high level of redundancy. KiwiRail said electrification would use less than 1% of Auckland's electricity capacity. KiwiRail also approached local lines company Vector about a possible third connection in the central city.

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