South Australia (SA1) experienced very high renewable penetration at 97.86% during the 13:00–13:30 period on 18 August 2026, with wind generation dominating at 1,952 MW and negligible solar and battery output. Prices across all five settlement intervals remained flat at negative $0.04/MWh, indicating oversupply relative to demand.
The negative price reflects excess renewable generation—particularly wind—relative to system demand, pushing marginal cost below zero. Multiple binding constraints with material marginal values (F_T+LREG_0050 at ~$24.92/MWh and F_TASCAP_RREG_0220 at $6.80/MWh) indicate that network or system security limits restricted further export or dispatch flexibility, preventing prices from falling further and preventing renewable curtailment that would otherwise have occurred.
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.