Tasmania experienced sustained negative pricing across three consecutive intervals on 21 September 2026, with prices reaching a low of -$13.87/MWh between 04:40 and 05:10. The negative pricing occurred during overnight hours with high renewable generation from wind (352–421 MW) and hydro (287–321 MW) contributing to oversupply conditions.
Negative pricing resulted from excess generation relative to regional demand during low-demand overnight hours, with wind and hydro resources generating substantially. A binding constraint with marginal values ranging from 36.91 to 45.62 $/MWh was active during these intervals, indicating physical or operational limitations constrained the region's ability to dispatch or export surplus generation, forcing the price floor downward to balance supply and demand.
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.