QLD1 experienced sustained negative pricing at −$1.31/MWh during the 22:00 settlement interval on 5 September 2026, with prices hovering near or below zero across multiple consecutive intervals. The region had substantial solar generation (3,967 MW combined) alongside significant coal baseload (3,263 MW), creating a structural oversupply condition during the evening transition period.
The negative pricing was driven by excess generation relative to demand during the early evening period when solar output remains elevated but demand has not yet recovered to daytime levels. The binding constraint F_T+RREG_0050 with marginal values between $3.44–$4.44/MWh indicates that a constraint was limiting the ability to export or redistribute this excess generation, forcing the marginal dispatch cost into negative territory as inflexible coal generation and substantial solar output could not be readily cleared from the region.
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.