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 [email protected].
Latest Report / More Information
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Current Storage Positions
Overview
National hydro storage remains above average, with levels having increased slightly from 110% to 113% of the historic mean for this time of year. North Island storage continues to be exceptionally high at 225% of the historic mean, while South Island storage is close to average at 105% of the mean.
This week’s insight covers high-level takeaways from the draft 2026 Security of Supply Assessment.
Security of Supply and Capacity
Energy
National hydro storage increased to 113% of historic mean at the end of last week.South Island storage increased from 102% to 105% and North Island storage increased from 221% to 225% with higher than average inflows for both islands last week.
Capacity
Residuals were healthy during morning and evening peaks last week. The lowest residual of 984 MW occurred during the evening of Monday 4 May which coincides with the highest demand peak of the week. A residual of 990 MW
occurred during the evening of Tuesday 5 May. All other residuals were greater than 1000 MW.
The N-1-G margins in the NZGB forecast remain healthy, but are trending downwards into winter with tighter spots appearing that we recommend the industry watch closely. 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 demand slightly increased from 758 GWh to 764 GWh. The highest demand peak of 5,874 MW occurred at 6:00pm on Monday 4 May.
Weekly Prices
The average wholesale electricity spot price at Ōtāhuhu last week dropped to $38/MWh from $101/MWh the week prior. Wholesale prices peaked at $136/MWh at Invercargill at 1:00am on Friday 8 May during a period of price separation
between the North and South Island. This coincided with the tripping of a synchronous condenser at Haywards resulting in reduced HVDC transfer limits during a period of southward transfer.
Generation Mix
Wind generation increased from 7% to 14% of the generation mix last week, above its yearly average of 10%. Hydro generation decreased from 59% to 53% of the mix and thermal generation remained at 6%, slightly below its yearly average of 7%. Geothermal generation slightly increased from 25% to 26%, continuing to sit above its annual average of 23% as seen in recent weeks due to the additional geothermal capacity at Ngā Tamariki and TOPP2.
HVDC
HVDC flows last week were predominantly northward with periods of southward flow occurring overnight. These periods coincided with high wind and lower hydro generation. Overall, 42 GWh was transferred north, while 29 GWh was transferred south during the week.
Consultations and Engagement
SOSA
Submissions on the Draft Security of Supply Assessment (SOSA) 2026 are open until 5pm Thursday 14 May, followed by a one‑week cross‑submission period. The SOSA provides a 10‑year outlook (2026–2035) on supply‑demand balance to
support security of supply risk management and investment decisions.
Emergency Reserve scheme
Expressions of interest are also open until Wednesday 20 May for an industry co‑design panel to support the development of the new Emergency Reserve ancillary service, enabled by recent Electricity Authority Code changes.
Industry Exercise
There is still time for electricity market participants to register for Industry Exercise 2026 to be held 20-21 May and we encourage all participants to get involved. It is an important opportunity to practice and test how you would respond to a major unexpected power system event.