South Australia (SA1) experienced sustained negative pricing at −$58.68/MWh for two consecutive intervals (22:45 and 22:55 on 9 September 2026), with prices oscillating sharply between negative and positive values within an eight-interval window. The region's generation mix was dominated by wind (1,374 MW) and solar (370 MW combined), with battery and gas generation providing supplementary capacity.
The negative pricing appears driven by binding constraints with significant marginal values, particularly constraint T_BLINK_TV_NGZ exhibiting a marginal value of $8.352 million, indicating substantial constraint-driven price suppression. The binding constraint F_T+NIL_MG_R6 (marginal value $19.38/MWh) suggests transmission or network limitations forced the market to accept negative prices to manage excess renewable generation, a typical occurrence when high wind and solar output cannot be efficiently exported or curtailed, compounded by the apparent inflexibility of other binding constraints in the dispatch solution.
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.