South Australia (SA1) experienced sustained negative pricing at −$6.02/MWh in one interval during the evening of 17 September 2026, with prices falling from $14.20/MWh to near-zero levels over a six-interval window. The region's generation mix was dominated by wind (985.72 MW) and solar (303.67 MW combined), contributing to oversupply conditions.
The negative pricing appears driven by high renewable generation exceeding local demand in SA1 during evening hours when solar output remained elevated (304 MW) and wind generation was substantial (986 MW). Binding constraints with positive marginal values—particularly F_T+LREG_0050 ($10.99/MWh) and multiple instances of F_T+RREG_0050 (up to $4.73/MWh)—indicate that dispatch was constrained by regulation service requirements, limiting the ability to curtail or absorb excess generation and forcing marginal bids increasingly negative to manage supply imbalance.
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.