QLD1 experienced sustained negative pricing at -$3/MWh across two consecutive intervals (21:00–21:05 on 19 September 2026), with prices declining from $22.85/MWh to negative territory. The negative pricing followed a period of very low prices ($0.85–$0.88/MWh) and occurred within a generation environment dominated by coal (3,816.75 MW) and solar (1,338.82 MW).
The negative pricing likely resulted from oversupply relative to minimum load requirements, with high coal generation and substantial solar contribution outpacing demand. Binding constraints with significant marginal values—particularly F_T+LREG_0050 ($40.99 and $15.99) and F_TASCAP_RREG_0220 ($4.97)—indicate supply-side network or reserve regulation constraints were active during the event, forcing generators to operate at negative prices to manage excess generation and meet constraint requirements.
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.