Summary
Security of Supply
National hydro storage increased by 4% to 92% of the historical average for the time of year. This pushes it further above the historical 10th percentile range. Heavy inflows in the North Island increased North Island hydro storage by 32% to 172% of the historical average. South Island storage increased less dramatically by 2% to 86% of the historical average for the time of year, as much of the rain would have fallen as snow.
The Maui full field outage finished on Sunday 19 June.
Weekly Demand
Demand increased from the week prior to 821 GWh. Cooler temperatures in the South Island and wild weather contributed to the increased demand. Demand peaked at 6,567 MW on Monday 13 June at 5:30pm, as the evening peak coincided with low temperatures in the South Island. Demand peaks continued to temper as the North Island experienced milder temperatures despite extreme wind and rain.
Generation Mix
This week saw continued high levels of renewable generation with 87% of the generation mix coming from renewable sources. This is slightly higher than the renewable generation percentage at this time of year in 2019. This included hydro generation, which increased from the week prior to 60% of the total generation mix, and wind generation, which comprised 8% of the generation mix.
Much of the thermal generation that is generally offered as base load has been two-shifting, turning on during the day and off overnight. Wind generation continued to be relatively high for the week due to wild weather except on Friday and Saturday (17 & 18 June), where thermal generation increased in response.
Weekly Prices
The average price continued to decrease, at Haywards it was $126/MWh. A decrease of 14% from $146 MWh the week before. Prices generally fluctuated between $250MWh and $100/MWh all week, with several periods of near $0/MWh prices. The price dips coincided with strong wind generation and low overnight demand.
Prices peaked at $307/MWh on Saturday 18 June at 12:00pm during a period of low wind generation and high demand.
HVDC
Transfer across the HVDC link over the past week again reflected typical winter conditions, with northward flow during the day and some periods of southward flow at night as a result of low demand.
Outages and Loss of Supply
There was one loss of supply event on Monday 13 June at 11:00 AM in Murchison, and another at Hinuera substation on Sunday 19 June.
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