Security of Supply Analysis

Scenarios for Potential Thermal Fuel Supply Disruptions

Under the SoSFIP clause 13.2, the system operator must develop and make publicly available scenarios for potential thermal fuel supply disruptions. We have carried out this analysis using our existing Electricity Risk Curve and Simulated Storage Trajectory framework to show potential future hydro storage under certain thermal fuel restriction scenarios. These analyses can be found in the links below.


Thermal Fuel Scenarios - September 2019 [ pdf 1.78 MB ]
Thermal Fuel Scenarios - March 2019 [ pdf 1.93 MB ]

What If

From time-to-time we will explore the possible impact of scenarios on the utilisation of hydro storage, the security of supply metric for energy production, given historic inflow sequences.  The base case for such scenarios will be the most recently published Simulated Storage Trajectories [ pdf 292.23 KB ] (SSTs) based on the same assumptions.

Possible gas restriction during 2020 HVDC outage

Prior to, and during, the 2020 HVDC outage there are a number of notified gas field outages that may reduce gas available for thermal generation stemming from either procurement choice or physical availability.  The following scenario has been modelled and projected SSTs depicted below.

Gas Field Outage When Modelled Generation Availability
Kupe 30 October - 27 November 2019


  • U5 231 MW
  • U6 27 MW
Generic 1 January - 24 April 2020 TCC 0 MW
Ahuroa Storage 7 - 23 February 2020 Stratford U1 and U2 0 MW
Pohokura - offshore field 11 - 24 March 2020


  • U5 308 MW
  • U6 36 MW

This scenario lifts the ERCs between 450 and 475 GWh in Feb and 260 and 290 GWh in March making their high point for this scenario March 2020. There is no major change to the height of the ERCs over June July the typical annual high point of the ERCs. The modelling shows that given current storage levels and assumptions during 2020 we are not expecting to cross any security of supply triggers even under a constrained gas scenario.

2020 HVDC and Gas Field Outages Simulated Storage Trajectories Graph [ pdf 242.44 KB ]