TAS1 experienced sustained negative pricing at −$0.58–0.59/MWh across two consecutive intervals (23:45 and 23:50 on 23 September 2026), following a sharp price spike to $30.20/MWh in the preceding two intervals. The negative pricing event was minor in severity and occurred during a period of elevated hydro generation (555.75 MW in the final interval) combined with steady wind output.
The negative pricing was driven by binding constraint F_TASCAP_RREG_0220 (marginal value $3.43–4.97/MWh), which became active during the high-generation period and constrained dispatch flexibility. The rapid transition from elevated prices ($30.20) to negative prices within five minutes suggests the constraint tightened temporarily, forcing the market into a position where marginal generation costs fell below zero—consistent with high hydro availability creating downward pressure on prices once the binding constraint's marginal value could no longer sustain positive clearing 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.