The industry comprises four key sectors:

1. Generation
There are six main generator businesses: Meridian Energy, Contact Energy, Genesis Power, Mighty River Power, TrustPower and Todd Energy. Generators are also entitled to sell electricity to consumers and energy retailers. Approximately 70% of New Zealand's electricity generation is hydro, with the balance from geothermal, gas, coal and oil-fired thermal stations, bio-mass plants and wind farms. Around 40 sites supply electricity to the national grid.

2. Transmission
Transpower (SOE) owns and operates the national electricity grid, which comprises switchgear, high voltage cables and pylons for transmitting high voltage electricity from generators to distributors. Transpower is responsible for transmitting high voltage electricity from the generating stations connected to the national grid to some 200 GXPs across New Zealand. These GXPs are the points of supply for distribution networks like Powerco.

3. Distribution
At the GXPs, or substations, electricity is transformed to lower voltages then conducted to end users by overhead wires or underground cables owned by local distribution companies. There are currently 28 of these, mostly regionally based, varying from publicly listed companies like Powerco to community-owned trusts. Powerco is New Zealand's second largest lines company by customer connections. The 1998 Electricity Reform Act requires retail, generation and distribution companies to be separate, preventing lines companies from being generators or retailers.

4. Retail
Retail companies sell delivered electricity to end-users.

There are currently six energy retailers in New Zealand:

• Meridian Energy
• Contact Energy
• Genesis Power
• Mercury Energy
• TrustPower
• Todd Energy