SA1 experienced sustained negative pricing for two consecutive 5-minute intervals (02:50–02:55 on 22 July 2026), with the minimum price reaching −$1.29/MWh. The region had substantial renewable generation (803 MW of wind and 605 MW of solar combined) alongside 138 MW of gas-fired CCGT generation and 119 MW of battery output, creating a structural supply surplus.
The negative pricing reflects a mismatch between high renewable generation and insufficient demand, compounded by inflexible committed plant. The binding constraint NSA_Q_GSTONE34_250 carried substantial marginal values (up to $19.48/MWh), indicating it actively constrained generation dispatch during the event, preventing efficient export or demand response mechanisms from clearing excess supply. The secondary binding constraint F_TASCAP_RREG_0220 (marginal values ~$6.8/MWh) also contributed to dispatch inflexibility, together driving marginal costs below zero to force down renewable and gas generation.
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.