Security of Supply
National hydro storage has decreased by two percent to 77% of average for the time of year, dropping just below the 90th percentile of its historical range. This is a result of below average inflows in both islands and consistent hydro generation.
North Island storage has decreased by 11% to 81% of average for the time of year. Much of this decline is due to Lake Taupo dropping to about 30% of full, which is typical for this time of year as the lake often operates at the low end of its range. South Island Storage has decreased by 1.5% to 77% of average for the time of year.
Demand increased slightly from the week before to 773 GWh. There were more distinct morning demand peaks in both Auckland and Wellington on Thursday and Friday as a result of the colder weather.
Demand peaked at 6,164 MW on Friday at 8:00am. This is the highest peak demand of the year to date signalling a shift in seasons.
With demand increasing the generation mix has remained relatively constant with the growth being shared evenly between hydro and thermal generation. Hydro generation was 428 GWh, while thermal generation continued to make up a large part of the remaining generation mix at 141 GWh. Wind generation increased marginally from the week earlier to comprise 6% of the generation mix.
Prices continued to hover around the $200 mark, reflecting the below average hydrology, and upward price pressure on thermal fuels including carbon.
The average price at Haywards was $224/MWh, a 7% increase from $209 MWh the week before. Prices peaked at Otahuhu at $807/MWh on Thursday 12 May at 8:00 am. This was driven by high demand, only 54MW of wind generation, requiring high levels of thermal generation over the morning peak. With some baseload thermal units not offering in the market, residual energy (generation offering into the market not being used) reduced to 150MW.
There was minimal price separation throughout the week.
HVDC was again more northward, with only a few periods of southward flow. Northward flow was higher on days with low North Island wind generation.