SA1 experienced two intervals of marginal negative pricing (-$0.1/MWh) on 16 June 2026 at 17:55 and 18:05, embedded within a period of near-zero pricing from 17:30 to 18:00. Wind generation dominated the supply stack at approximately 1,460 MW, with minimal contribution from solar and battery resources, creating an oversupply condition during low-demand evening periods.
The sustained near-zero and negative pricing reflects excess renewable generation relative to regional demand during the early evening, when solar output had ceased but wind remained elevated. Binding constraint F_MAIN+RREG_0220 held marginal values between $3.43 and $4.04/MWh across the window, indicating an active constraint limiting export or dispatch flexibility; the constraint binding at positive marginal values whilst prices approached zero suggests that the constraint prevented generators from withdrawing surplus wind generation, forcing continued low-cost dispatch that depressed the regional price floor.
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.