The week of 31 May to 7 June 2026 delivered a textbook late-autumn NEM — characterised by strong wind resource across South Australia and Victoria, repeated bouts of oversupply-driven negative pricing, and a sustained but mysterious binding constraint in Tasmania that attracted attention well beyond its regional price impact. Demand across the NEM tracked seasonally cool conditions, with morning peaks moderate and overnight troughs deep enough to push multiple regions into negative territory on several occasions. By mid-week, a tightening in gas commodity prices added upward pressure to afternoon and evening spot prices, particularly in SA and NSW, before easing into the weekend.
In Western Australia, the WEM had a notably active week. Three material price spikes — reaching $361/MWh on 3 June, $347/MWh on 3 June evening, and $263/MWh on both 5 and 3 June — punctuated an otherwise elevated baseline averaging well above $100/MWh for most of the week. The WEM's week-average ranged from $103/MWh to $136/MWh across the period, reflecting tight supply margins during overnight and morning periods when solar generation is unavailable and system reserves are leaner. The contrast with some NEM regions — where daily averages dropped as low as $7/MWh (VIC1, 3 June) — underscores the structural differences between the two markets.
Across the NEM, South Australia and Victoria consistently recorded the lowest daily averages, with SA1 dipping to $12/MWh on 2 June and VIC1 touching $7/MWh on 3 June, driven by strong overnight wind and midday solar oversupply. Queensland and NSW held firmer through the week, finishing closer to $60–$87/MWh by week's end as heating demand lifted. Tasmania traded in a relatively narrow band of $80–$87/MWh for most of the week, anchored by its hydro-dominated dispatch stack.
Spot price outcomes were highly variable across regions and days:
The WEM was the week's most consistently elevated market. Daily averages ranged from $103/MWh (31 May) to $136/MWh (5 and 4 June), with the week's peak reaching $372/MWh on 3 June evening. Three separate trading intervals breached $250/MWh across the week — on 3 June (morning, $361/MWh; evening, $347/MWh escalating to $370/MWh), 5 June ($263/MWh overnight), and 6 June ($251/MWh mid-morning). These spikes were single-interval in duration but reflect recurring tightness in overnight and shoulder periods. Even on quieter days, WA1 floor prices held above $47/MWh — substantially firmer than NEM equivalents.
Tasmania achieved 100% renewable penetration on every evening from 1 June through 7 June, a sustained run driven by hydro baseload — ranging from approximately 650 MW to 2,680 MW depending on the dispatch period — supplemented by wind. Prices during these periods remained stable at $77–$87/MWh, indicating the grid managed supply-demand balance without material distortion. Notably, no gas-fired generation was required during these windows.
South Australia delivered several high-penetration episodes across the week: 95.5% on 1
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