Security of Supply and Capacity
Energy
National hydro storage continues to be above the 90th percentile of historical ranges for the time of year at 127%. Manapouri storage continues to sit above its operating range indicating spill. With a significant rain event expected in the coming days we expect hydro storage to increase further.
Capacity
Friday morning saw residuals drop to 160MW due to low wind generation, high demand, limited thermal capacity being offered and a short notice outage on a thermal peaker.
Our NZ Generation Balance planning tool currently shows several days across August and September where there could be a potential generation shortfall if two major assets on the grid were to fail.
Electricity Market Commentary
Weekly Demand
National demand increased to 880 GWh, 57 GWh higher than the previous week. This is the greatest weekly national demand we have seen over the last four years.
Last week cold weather reached the upper North Island where load is more sensitive to temperature due to population size and lesser amount of controlled load compared to other regions. This kept loads high from Monday to Friday. Every Monday to Thursday evening peak was above 6500MW, and on Friday the morning peak was the second highest on record at 6890MW. This was second to the 9 of August 2021 morning peak of 6917MW. It is important to note that evening peaks are generally higher than morning peaks.
Generation Mix
The proportion of both hydro and thermal generation increased from the previous week to comprise 66% and 9% of the energy mix respectively. Wind generation decreased from the previous week to comprise 6% of the energy mix. Wind generation was high at the start of the week and picked up again on Sunday.
On Friday morning three rankines ran for a short period of time to help meet the evening peak.
Weekly Prices
The average prices at Haywards was $94/MWh. With high demand across the whole week, prices lifted to the $150/MWh range and spiked on Friday morning to $480/MWh as demand was high and generation was tight. There continues to be prolonged periods of prices near $0/MWh when wind was strong combined with low night demand.
HVDC
HVDC transfer was entirely northward this week as a result of high North Island demand, high South Island hydro generation and low North Island wind generation. Peak transfer was 832 MW northward on Friday 12 August to support high North Island morning peak demand.
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