South Australia (SA1) experienced sustained negative pricing, reaching −$1.10/MWh in the 22:00 settlement interval on 11 September 2026, with negative prices persisting across two intervals. Prices declined sharply from $10.52/MWh at 21:30 to negative territory by 21:55, despite moderate total generation.
The negative pricing was driven by a binding constraint (I_CTRL_ISSUE_BL) with a marginal value of $26.912 million, which actively restricted system operation during both intervals. High wind generation (1052.31 MW) combined with solar contribution (193.11 MW combined) created excess generation that could not be economically or technically dispatched under the constraint, forcing prices negative to incentivise demand response and reduce output.
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.