Transpower does not own any generation capacity and cannot control how much electricity is offered to the system; this is a matter for generators acting in response to forecast demand and price signals.
However, in our system operator role, we work closely with industry to understand whether there is enough electricity generation and transmission capacity to power New Zealand now and into the future.
Long-term view of security of supply
Our annual Security of Supply Assessment looks at the balance between supply and demand in the electricity system over the coming decade. It provides a clear view of the generation and transmission capacity the country is expected to need into the future. This helps generators, other market participants, investors and stakeholders understand security of supply risks and assists their decision making over things like building new generation and transmission lines to meet future demand.
This annual assessment covers a range of scenarios, such as how fast demand is growing and how quickly the sector switches away from carbon-based fuel sources like coal and gas. It includes two key measures - energy margins and capacity margins.
Energy margins tell us whether there is enough fuel in the system to power the country over a period of time, such as the coming winter. It includes water in the hydro lakes, wind, solar and geothermal generation capacity, and whether there is sufficient gas, diesel and coal stockpiles to run our thermal generators when they are needed.
Capacity margins look at whether there is enough generation capacity to power New Zealand at any given point in time, including whether there is sufficient transmission capacity to deliver electricity to where it is needed, when it is needed. New Zealand is a long and thin country with most of our hydro capacity in the South Island and the bulk of electricity demand in urban centres in the North Island, which poses unique challenges.
Near-term security of supply reporting
We also publish detailed charts and graphics related to security of supply information for market participants every Tuesday in our Market Operations Weekly Report. This includes information on lake levels, the contribution of all fuel types to total electricity generation, capacity margins over the previous week and for the months to come, as well as trends in demand and wholesale prices.
Our Electricity Risk Curves are updated every month to provide industry an indication of the risk of running out of hydro storage over the next 12 months, taking into account the assumed availability of generation, fuels like coal and gas, as well as the impact of hydro inflow variation on hydro storage levels over time.
Our relevant security of supply reporting and other related information can all be accessed from this webpage.
Real-time matching of supply and demand
As we get within a week of real time, our National Coordination Centre (NCC) forecasts expected electricity demand and generators offer electricity to meet this demand throught the wholesale electricity market. Find out more about how the market works here.
The market schedules show more accurate demand forecasts, generation offers, and the bids made by retailers to buy the electricity that they distribute to electricity consumers. Taken together, the market schedules show whether there is sufficient generation to meet demand throughout the week ahead.
A range of live power system and market data is also available here.
Capacity and outage planning
Our New Zealand Generation Balance (NZGB) planning tool helps us identify whether generation and transmission capacity is sufficient to meet peak demand over the coming six months throughout the country. It takes into account outages for necessary maintenance work as well as unplanned equipment outages when there is a fault.
We also provide a Planned Outage Coordination Process (POCP) tool to help generators, lines companies and Transpower as the operator of the national grid coordinate these necessary maintenance outages. This work is necessary to keep the system humming and minimise unplanned outages from faults.