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
The decrease in New Zealand hydro storage was arrested with inflows from a recent storm. However, it remains below the 10th percentile for this time of year at 77% of the seasonal mean. South Island storage is lower at 73% of the seasonal mean.
In this week’s insight we look at the effect of time-of-use plans on power usage peaks.
Security of Supply and Capacity
Energy
New Zealand hydro storage remains below the 10th percentile for this time of year. Storage remained at 77% of average due to the recent storm cycle bringing some inflows. South Island hydro storage dropped slightly from 74% to 73% of historic mean and North Island storage increased slightly from 103% to 104%.
Our August monthly Energy Security Outlook was published last week. The risk curves have not changed substantially since the July update. Our scenario shows that retaining all three Huntly Rankine units significantly reduces the energy risk in 2026.
Capacity
Capacity margins were extremely healthy last week with residual at all peaks exceeding 1,100 MW. The lowest residual occurred on the morning of 25 August, at 1,105 MW. This was due to high thermal commitment and increased wind.
The N-1-G margins in the NZGB forecast are healthy through to late October. 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 last week decreased significantly from 881 GWh the week prior to 821 GWh, which was similar to what we have previously seen at this time of year. The highest demand peak occurred at 7:30 am on Monday 25 August, at 6,334 MW which was 610 MW lower than the previous week's highest peak. This was due to higher temperatures.
Weekly Prices
The average wholesale electricity spot price at Ōtāhuhu last week decreased to $148/MWh from $218/MWh the week prior in line with wind generation returning to the 52-week average. Wholesale prices peaked at $398/MWh at Invercargill at 8:30 pm on Friday 26 August due to a grid constraint.
The Ruakākā battery has added significant reserve capacity to the market which has helped keep reserve prices low in recent weeks. A spike in South Island Fast Instantaneous Reserve price occurred on 31 August at 1:30 am to $57/MWh. This was caused by the HVDC setting the risk during south flow.
Generation Mix
Hydro generation contributed 53% of the generation mix last week, lower than the previous week and the average for the past 52 weeks. Wind generation increased from 6% to 9% of the mix, matching its average contribution. Thermal generation remained similar at 13%. The geothermal share increased slightly from its average of 22% to 23% of the mix.
HVDC
HVDC flow last week started mostly northward with overnight periods of southward flow before later in the week transitioning to mostly southward flow. Southward flow was caused by South Island hydro generation reducing and wind generation increasing. In total, 19 GWh was sent north and 18 GWh was sent south.
CACTIS Consultation Open
Consultation to seek feedback on the proposed Connected Asset Commissioning, Testing and Information Standard (CACTIS) opened on 1 September. The closing date for submissions is 29 September. More information on this consultation can be found here.