TAS1 experienced sustained negative pricing of approximately $-10/MWh across two consecutive settlement intervals (21:55 and 22:00 on 11 September 2026), following a sharp price spike to $85/MWh in the preceding periods. The negative pricing occurred during a period of elevated hydro generation (around 1000 MW) combined with modest demand, creating an oversupply condition in the region.
The binding constraint I_CTRL_ISSUE_BL with a high marginal value of $26.912 million was active during the negative price intervals, indicating a constraint was preventing efficient dispatch and forcing generators into a situation where the marginal price turned negative. The substantial hydro generation (980–1028 MW) during this period, combined with relatively modest total demand, created excess supply that could not be efficiently exported or curtailed, driving prices below zero as the dispatch algorithm sought to reduce generation through negative pricing signals.
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.