Security of Supply and Capacity
Energy
National hydro storage remains very high at 148% of the historical average for this time of year, a 2 percentage point decrease on last week. Nationally the lakes are at 91% of full, with the North Island at 87% of full and South Island 91% of full.
Inflows for both islands remained above average for the week. Over the past four weeks inflows have been 139% of average in the North Island and 203% of average in the South Island.
Capacity
Last week's generation capacity was tight at several points. The lowest residual was observed on the evening of Tuesday 6 September, at 60MW, due to the high demand, low wind generation and some slow start thermal capacity being unoffered or on outage. This is covered in more detail in the insight.
Both of the mornings of the 7th and 8th saw dispatch schedules with less than 200MW of residual.
As we move further into spring and peak demand drops away, our NZ Generation Balance planning tool now indicates that there are no potential generation shortfalls over the next 200 days. Please click here for more information.
Electricity Market Commentary
Weekly Demand
National demand increased on the previous week to 843 GWh due to the cold temperatures across the country. Demand peaked at 18:00 on Monday 5 September at 6,727 MW, but residuals were comfortable for this period, aided by a large amount of wind generation. Peak demands were high through to Wednesday afternoon before dropping off as the weather warmed.
Weekly Prices
Prices spiked regularly over the week as high demand called on higher priced generation to clear. There was six trading periods with prices above $500/MWh and nearing $1000/MWh. The highest prices occurred on the evening of the 6th at $1,687/MWh at Haywards. Sustained reserve prices reached ~$1,500/MWh for this period in both islands. Outside of these periods, prices remained mostly under $100/MWh. The average price at Haywards was $84, up from $7 last week.
Generation Mix
The proportion of hydro remained high at 70% of the generation mix due to the high storage and inflows, whilst wind generation dropped to 4% of the mix. The average contribution of renewable generation remained high at 91% of the generation mix for the week, with thermal generation making up 6.6%. This was an increase on previous weeks due to the reduction in wind generation and the high demand peaks requiring additional thermal generation.
HVDC
HVDC transfer was, again, entirely northward last week reflecting high hydro storage and South Island hydro generation and low North Island wind generation. Peak transfer was 937 MW northward on Monday afternoon at 14:30.
Price Separation
There were three periods of intra-island price separation in the North Island on Monday as a binding transmission constraint on Redclyffe-Tuai led to reduced prices at Tuai.
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