QLD1 experienced sustained negative pricing at approximately −$2.88/MWh across two consecutive settlement intervals (20:55–21:00) on 18 September 2026. This occurred during high solar generation (1,071 MW) and moderate wind output (334 MW) in the evening period, following a sharp price decline from $64.83/MWh earlier in the half-hour.
The negative pricing was driven by a constraint with a marginal value of $89.82 (F_T+LREG_0050), which significantly exceeded the spot price floor and forced dispatch patterns that generated surplus supply in QLD1. High renewable generation combined with the binding constraint on lower-bound regulation services created a mismatch between scheduled output and system requirements, necessitating negative prices to incentivise demand response and generation withdrawal.
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.