QLD1 experienced sustained negative pricing at −$6/MWh across five consecutive intervals (03:25–04:00 on 18 September 2026), a minor severity event. High solar generation (approximately 5,400 MW combined) and moderate coal output (2,683 MW) during early morning hours created an oversupply condition relative to regional demand.
The negative prices were driven by constraint binding_constraint F_T+LREG_0050, which showed declining marginal values from $104.90 to $27.58 across the event window, indicating progressively tightening constraint pressure. The high solar contribution during daylight hours combined with inflexible coal generation created excess supply that generators were unable to reduce, forcing prices negative as the binding constraint prevented efficient dispatch rebalancing.
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.