South Australia (SA1) experienced sustained negative pricing at $-3/MWh across two consecutive intervals (17:10 and 17:30 on 18 June 2026), with prices remaining slightly negative across an 8-interval window from 17:05 to 17:40. The generation mix was dominated by wind output of 1,695 MW with minimal load or demand for available supply.
The negative pricing reflects oversupply conditions where wind generation substantially exceeded regional demand, requiring prices to turn negative to incentivise increased consumption or curtailment. Multiple binding constraints with material marginal values—particularly constraint F_T+LREG_0050 at $26.74/MWh and constraint F_MAIN+RREG_0220 at $4.68/MWh—indicate network or regional limitations preventing efficient dispatch of excess wind capacity, trapping generation and driving the price floor downward.
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.