NSW1 experienced two consecutive intervals of negative pricing at -$6.76/MWh on 17 September 2026 at 03:15 and 03:20 AEST, representing a minor severity event. This occurred during a period of high solar generation (3,342.7 MW) and significant coal output (3,001.9 MW), with prices recovering to modestly positive levels in surrounding intervals.
The negative pricing reflects an oversupply condition where generation substantially exceeded demand during the early morning period. Several binding constraints with material marginal values (F_T+LREG_0050 at $14.27/MWh and F_TASCAP_RREG_0220 at $4.68–$4.99/MWh) indicate that network or reserve requirements were limiting the ability to dispatch additional supply, forcing the system to accept negative prices to manage excess generation. The high solar output combined with inflexible coal generation likely contributed to the supply–demand imbalance that necessitated these pricing outcomes.
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.