South Australia (SA1) experienced very high renewable penetration of 94.5% during the evening of 18 September 2026, driven predominantly by wind generation (605.5 MW) and solar output (194.17 MW combined). This high renewable contribution resulted in negative electricity prices ranging from −$7.77 to −$16.95/MWh across the settlement period, indicating an oversupply of generation relative to demand.
The negative pricing reflects the fundamental mismatch between abundant renewable generation and lower evening demand, forcing generators to pay for dispatch. The binding constraints with marginal values of $18.35 and $3.99–$3.67/MWh indicate that transmission or network-related limitations were active in restricting supply flows, preventing the region from fully exporting surplus renewable generation and thereby amplifying the downward pressure on spot prices.
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.