VIC1 experienced sustained negative pricing at approximately −$69/MWh across three consecutive intervals on 20 September 2026 at 02:45–03:10 UTC, with prices recovering only slightly to −$60/MWh before declining again to −$68.98/MWh. The negative pricing persisted despite a substantial generation mix comprising 1205.56 MW of wind, 198.21 MW of solar, and 1604.97 MW of brown coal generation.
The negative pricing was driven by binding constraints with material marginal values, particularly constraint F_T+LREG_0050 (marginal values of $49.97 and $35.79/MWh), which constrained the region's ability to dispatch or export excess generation during the off-peak overnight period. The high inertial and ramp-rate regulation constraint marginal values (F_I+RREG_0220 and F_T+RREG_0050) indicate that system security requirements further restricted available dispatch capacity, forcing the market price into the negative domain to incentivise reduced generation or increased consumption as the binding constraint mechanisms took precedence over standard merit-order dispatch.
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.