South Australia (SA1) experienced sustained negative pricing at −$4.32/MWh across two consecutive five-minute intervals (23:45 and 23:50 on 6 September 2026), with the broader 2-hour window showing sporadic negative excursions. The region was operating with high renewable generation (443–794 MW from wind and solar) and minimal battery storage dispatch, creating conditions of excess supply relative to local demand.
The negative pricing was driven by a binding constraint (F_T+LREG_0050) with marginal values ranging from $17.05 to $21.37/MWh, indicating the constraint was actively limiting generation export or imposing a cost on the region's supply stack. The combination of substantial wind (794 MW) and solar output (392–444 MW) with zero battery charging and minimal flexible gas generation (0.11 MW OCGT) left the market unable to economically absorb or dispatch the surplus generation, forcing marginal generators to operate at negative prices to clear supply.
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.