SA1 experienced sustained negative pricing at $-0.55/MWh across two consecutive intervals (16:30–16:35) on 18 September 2026, following a period of zero or near-zero pricing. The region was characterised by high wind generation (1,387.61 MW) and modest battery charging (31.97 MW combined), with minimal conventional thermal output.
The negative pricing reflects an oversupply condition in SA1 during low-demand evening hours, driven by elevated wind generation that exceeded regional load requirements. A binding constraint with a marginal value of approximately $89.85 (constraint_id: F_T+LREG_0050) was consistently active across the pricing period, indicating that a network or regional limitation forced the dispatch stack to include lower-priced or negatively-priced bids to manage the excess generation, resulting in the negative settlement prices.
Causal analysis generated by gridIQ's synthesis model from live AEMO market data: dispatch prices, generation mix, interconnector flows and market notices in the interval surrounding the event.