What we do

Transpower owns and operates the National Grid – or high voltage transmission network – that carries electricity around the country. This network includes over 12,000 km of transmission lines and 170 substations.

These transmission lines and substations transport bulk electricity (up to 220,000 volts) from where it is generated (by companies like Contact Energy, Meridian Energy, Genesis Energy, Mercury Energy, and Trustpower) to cities, towns and some major industrial users (like New Zealand Steel and the Tiwai Point Aluminium Smelter). It also connects with smaller lines companies who package and deliver that power to the doorsteps of New Zealand’s homes and businesses.

As a transmission company and State-Owned Enterprise (as of 1994), our role is to build, operate and maintain the grid, and does not include generating, owning or selling electricity. Generators and lines companies pay us to use our assets, but by the time the power gets to your home or business we make up just a small proportion of your electricity bill – on average around 9%.

Because our transmission network is a natural monopoly, our investments and transmission charges are regulated by the Commerce Commission.

Maintaining our assets

Much of New Zealand’s electricity (80-85%) is generated from renewable energy sources (hydro and increasingly wind) that exist in remote areas, a long way from where many people live.

Part of providing a strong National Grid is to enable the development of new energy generation and ensure the transmission of electricity to where it is needed.

To do this effectively, it’s important that assets such as transmission towers, lines, and conductors are in a good state.

The current ‘backbone’ of the National Grid was mostly built in the 1950s and 60s and, in places, is now nearing its capacity. It is Transpower’s role to manage the long-term stability of the Grid as electricity demand that is predicted to grow over the next 40 years, and the subsequent need to connect a diverse range of new sources of generation, leaves Transpower with a major investment programme to address.

Managing New Zealand's power system

As System Operator, Transpower manages the power system in real time to ensure energy is flowing to where it is needed: 24 hours a day, 7 days a week.