Generation Mix

Coal, gas and oil-fired (collectively 'thermal') generation typically make up about 20-25% of New Zealand's total annual electricity supply.

Geothermal, co-generation and wind collectively contribute about 20%. Thermal output varies from year to year and season to season depending on hydro storage and inflows. In extended dry periods more thermal generation is needed to conserve hydro storage.

No generator is 100% reliable. When major thermal generators are unavailable for an extended period, there can be an adverse effect on security of supply.

Generation Mix

The table below gives the breakdown of generation sources for the last three months.

Generation Source Energy Last 13 Weeks (GWh) Energy Last 4 Weeks (GWh) Energy Last Week (GWh) Change this week to last week


82 20 0
Geothermal 1941 611 155 4
Hydro 5785 1862 485 25
Thermal 1625 434 98 -22
Wind 438 149 55 24

Thermal Plant Availability

The above graph shows planned thermal capability (columns) over the next six months, compared to maximum capability (line). Planned capacity is maximum capacity adjusted for planned outages (times when thermal stations are expected to be out of service for maintenance).

Actual thermal output in any given month will be a percentage of the total capacity installed, reflecting market conditions at the time, available fuel, unplanned outages, any transmission constraints, and system operation requirements.

Thermal generation availability is forecast to be normal over the next few months.

Geothermal generation is not included in the graph.