Our Market Operations Weekly Report contains the latest information about the electricity market, including security of supply, wholesale price trends and system capacity.
It is published every Tuesday. Click here to receive the report via email every week.
If you have any comments or questions please contact the Market Operations Team at Market.Operations@transpower.co.nz.
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Current Storage Positions
Overview
National hydro storage has dropped again this week and sits in the bottom 7% of historic ranges. The March Energy Security Outlook has been published which included updates to the Electricity Risk Curves (ERCs) and Simulated Storage Trajectories (SSTs).
In this week's insight we take a look at how this year's supply pipeline compares to last year's, using information for the 2025 Security of Supply Assessment.
Security of Supply and Capacity
Energy
New Zealand hydro storage decreased from 81% to 77% of the historic mean last week. South Island hydro storage decreased from 80% to 77%, while North Island storage dropped from 89% to 81% of the historic mean for this time of year. National storage now sits below the 7th percentile, while South Island storage sits below the 6th percentile.
Lake levels at Manapōuri and Te Anau remain low, but have improved slightly over recent weeks. The System Operator continues to monitor the situation and is ready to request a grid reconfiguration from the Grid Owner if the low lakes result in a loss of generation flexibility that risks system security. Further details can be found on our website.
Capacity
National capacity margins were healthy last week, with over 1,000 MW available during all peaks. This is because thermal unit commitment is high for this time of year in response to low hydro storage. The lowest residual was 1,264 MW on Tuesday morning.
The N-1-G margins in the NZGB forecast are healthy through to end of May. Within seven days we monitor these more closely through the market schedules. The latest NZGB report is available on the NZGB website.
Electricity Market Commentary
Weekly Demand
Total weekly demand decreased by 7 GWh to 714 GWh last week. This is slightly below typical loads at this time of year based on recent years. Demand peaked at 5,124 MW at 8:00am on Friday 28 March.
Weekly Prices
The average wholesale electricity spot price at Ōtāhuhu last week increased to $327/MWh from $256/MWh the week prior. Wholesale prices at Ōtāhuhu peaked at $464/MWh on Wednesday 26 March at 5:00pm coinciding with a period of low wind generation (only 28 MW).
Generation Mix
Wind generation decreased to 5% of the mix from 11% the previous week while hydro generation increased to 47% from 41% to fill the gap. The thermal generation contribution remained steady at 20%, with two Rankine units on outage, and geothermal remained steady at 25%.
HVDC
HVDC flow reversed to predominantly northward last week with an increase in hydro generation. There were some periods of southward transfer coinciding with overnight periods of low demand and high North Island thermal generation. In total, ~18 GWh was sent North and ~13 GWh was sent south.
SOSFIP Review Issues Paper
Thanks to those who submitted submissions and cross-submissions on the SOSFIP Review Issues Paper. All submissions and cross-submissions are now published and can be found at Security of Supply Forecasting and Information Policy (SOSFIP) Review Issues Paper.