Tasmania experienced two intervals of negative pricing on 20 September 2026 at 09:05 and 09:15 (settling at −$4.87/MWh and −$3.12/MWh respectively), following a period of elevated prices. The negative prices occurred within a context of high renewable generation, with combined hydro and wind output ranging from approximately 850 MW to 975 MW during the affected period.
The negative pricing was driven by binding constraints with significant marginal values, particularly constraint F_T+LREG_0050 which exhibited marginal values between $25.89/MWh and $30.77/MWh across multiple intervals. The binding constraint framework, combined with sustained high renewable generation output (hydro and wind collectively dominating the generation mix), forced dispatch conditions where additional generation became economically unviable, pushing prices negative as the market required participants to absorb surplus renewable output.
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.