SA1 experienced sustained negative pricing at approximately −$20/MWh across three consecutive intervals (22:15–22:25) on 18 September 2026. Prices gradually declined from −$12.17/MWh at 21:55, reaching a trough of −$20.42/MWh before stabilising around −$20/MWh thereafter.
High renewable generation (wind at 449 MW and solar at ~335 MW combined) coupled with modest gas generation (42 MW CCGT, 0.2 MW OCGT) created structural oversupply in the region during evening peak solar decline. Binding constraints with significant marginal values—particularly F_T+RREG_0050 at $282.59/MWh and F_TASCAP_RREG_0220 varying between $3.99–$6.33/MWh—indicate active network or regulation service constraints limiting relief exports or demand-side response, forcing prices into the negative territory to balance supply.
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.