Commodity Demand — SA1: Friday 18 September 2026
South Australia's spot price sits at $0.01/MWh at 6:30am AEST, with demand at 1,287 MW — a level that has repeatedly capped price near zero or negative overnight as 1,336 MW of wind generation swamps the region's needs. Wind is currently supplying more than total demand, with the surplus exported via interconnector, consistent with the 96.9% renewable share and 0.015 tCO2/MWh carbon intensity recorded in the latest interval. This wind-driven oversupply pattern has dominated the past 24 hours: demand troughed below 100 MW around 3:30am, dragging prices to -$180/MWh, before climbing through the morning ramp to a peak near 1,608 MW at 9:15am, which lifted prices briefly to the $40-80/MWh band.
The price-demand relationship today is unusually loose because wind output, not load, is setting the marginal price. Demand swings of 1,000+ MW between overnight trough and morning peak produced price swings from -$180/MWh to +$96/MWh over the past 24 hours, but the current 1,287 MW demand level is only producing a flat $0.01/MWh print — confirming wind is still oversupplying the region even as load recovers into the morning shoulder. Traders should watch the 8-11am window, where demand historically climbs past 1,600 MW and prices have shown more sensitivity, spiking above $50/MWh when wind eases relative to load.
The critical factor for today's outlook is AEMO's Minimum System Load (MSL1) notice for SA: forecast demand is expected to fall below -40 MW between 11:30am and 2:30pm, with a minimum of -178 MW forecast at 1:30pm. This is a negative operational demand event driven by rooftop solar and wind combined exceeding underlying consumption, and it aligns with the load-shifting windows flagged in the forecast data — five separate low-price windows overnight and into tomorrow morning offering savings of $136-228/MWh versus peak for flexible load. AEMO has already directed AGL's Torrens Island unit to remain synchronised for voltage support through 5pm today, reflecting the system strength challenge that accompanies these high-renewable, negative-demand periods.
Forward price data confirms the pattern: forecast RRP swings from -$176/MWh around 3:30am tomorrow to +$80/MWh near 9am tomorrow, tracking the same solar/wind-versus-demand dynamic. With clear skies (0% cloud cover) and 12.3°C conditions today, expect solar to reinforce the midday demand suppression, keeping prices compressed or negative through early afternoon before the evening ramp — historically 5-8pm — reasserts price sensitivity to demand as solar drops away.