Seeking feedback on Security of Supply Annual Assessment sensitivities

Feedback required by 6 December 2019

The System Operator is requesting your feedback on the scenarios and sensitivities it uses in the Security of Supply Annual Assessment. Each year, the System Operator produces analysis of the supply/demand balance over the next 10 years. This analysis is limited to 3-4 core scenarios, and also includes a number of sensitivities that can be used to examine possible variations to future supply and demand forecasts. As an example of this, the results from the 2018 Annual Assessment are presented in the Annual Assessment Webtool, where you can select a scenario (e.g. low demand), and apply any combination of different sensitivities (such as Tiwai Early Exit or Thermal Decommissioning).

The proposed scenarios and sensitivities in this year’s analysis will look similar to last year but with a few changes:

Proposed scenarios for the 2020 Annual Assessment:

  1. Low demand
  2. Medium demand
  3. Thermal constrained

Proposed sensitivities for the 2020 Annual Assessment:

  1. High Demand - This sensitivity explores the situation where demand growth is higher than anticipated.
  2. Tiwai Exit - This sensitivity explores the situation where the NZAS aluminium smelter starts reducing its output from 2022 and closes at the end of 2023. Last year, this sensitivity was coupled with the assumption that the Rankine units at Huntly would shut at the same time. This year we will only consider the impact of Tiwai decommissioning in this sensitivity. This sensitivity can be combined with the thermal constrained scenario to understand the impact of Huntly Rankines decommissioning at the same time.
  3. Thermal decommissioning - This sensitivity explores the situation where one of the two Combined Cycle Gas Turbines shuts down in 2022.
  4. Delayed build time - This sensitivity explores the situation where the commissioning date for new generation is delayed by 1 year.
  5. High peak demand – This represents slow uptake in load management relative to EV uptake, or changes in load management by distributors as a result of changes in transmission pricing
  6. Potential grid connected solar – This reflects that Gird connected solar can be consented built and connected much more rapidly than traditional rotating generation.

We are interested in your responses to the questions below:

  1. What sensitivities did you find most useful in the past?
  2. Are there any sensitivities that you think we should include in the upcoming annual assessment in addition to the ones above?
  3. Have you used the webtool, was it useful?
  4. Any other comments?

Please email responses or feedback by 6 Decemeber 2019 to