QLD1 experienced sustained negative pricing over three intervals on 20 September 2026 at 02:25–02:50 AEST, with prices ranging from −$8.77/MWh to −$10.60/MWh. The event occurred during high solar generation (1,126–1,140 MW) combined with substantial black coal output (2,520 MW), creating a supply surplus in the region.
The negative pricing was driven by excess generation that could not be readily exported or curtailed, forcing marginal generators to pay for dispatch. Multiple binding constraints with positive marginal values (F_T+LREG_0050 at $49.97/MWh, F_T+RREG_0050 at $2.80/MWh, and F_I+RREG_0220 at $2.58/MWh) restricted the region's ability to relieve the surplus, preventing normal price recovery mechanisms and pushing the market into negative pricing as a mechanism to manage minimum generation levels and network security 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.