SA1 experienced sustained negative pricing at -$7/MWh over three intervals on 15 September 2026 at 22:40–23:15, with prices progressively declining from -$5.22 to -$7/MWh. The region had high renewable generation (1,172 MW wind, 366–275 MW solar) and minimal demand flexibility (zero battery storage) during the evening shoulder period.
The negative prices reflect a supply surplus driven by substantial wind and solar output during low-demand evening hours with insufficient flexible generation or storage to absorb the excess. The consistent binding of constraint F_TASCAP_RREG_0220 with marginal values of $4.95–$4.99/MWh, along with F_T+RREG_0050 at $3.79/MWh, indicates physical network or system security limits restricted the dispatch of flexible plant, forcing the market clearing point below zero as generators had to accept payment reductions to remain dispatched rather than trip or curtail.
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.