Transpower was initially formed as an operating division of the Electricity Corporation of New Zealand (ECNZ) in 1987.

[2] The New Zealand national grid provides the means of transporting bulk electricity from where it is generated (by companies like Meridian Energy and Mercury Energy) to cities, towns and some major industrial users like the Tiwai Point Aluminium Smelter.

Transpower also owns and operates the HVDC Inter-Island, a 611-kilometre (380 mi) ±350 kV high-voltage direct current link between the two islands.

The system operator is required to maintain a continuous (second-by-second) balance between electricity supply from power stations and demand from consumers, and also ensure the provision of reserves that will allow for sudden contingencies.

In addition to its roles of real-time dispatch of generation and managing security, the system operator also carries out investigations and planning to ensure that supply can meet demand and system security can be maintained during future trading periods.