South Australia (SA1) experienced sustained negative pricing at approximately -$2/MWh across two intervals on 4 September 2026, with the deepest trough at -$4.37/MWh. The region was generating substantial renewable output, particularly 1,625 MW of wind generation, during an early morning period of low demand.
The negative prices were driven by surplus renewable generation relative to regional demand, with wind output at high levels creating downward pressure on the spot price. Binding constraints with significant marginal values (constraint F_T+RREG_0050 at approximately $5.40–5.42/MWh and F_TASCAP_RREG_0220 at $4.30/MWh) indicate that network constraints limited the ability to export excess generation out of the region, forcing in-region solar and wind to bid down to negative levels to maintain dispatch.
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.