South Australia experienced sustained negative pricing in SA1 during the 18:05–18:40 settlement period on 12 June 2026, with prices reaching a minimum of −$12.83/MWh before recovering to around −$3/MWh. The episode reflected a period of excess generation relative to demand, with wind generation contributing over 1,000 MW to the region's supply.
The negative pricing was driven by high wind generation (1,054.87 MW) coinciding with low demand, creating a supply surplus that required prices to fall below zero to incentivise load or dispatch curtailment. Binding constraints on raise and regulation services—particularly those with marginal values between $4.35 and $6.80/MWh—indicate that the system was concurrently managing tight ancillary service requirements, which constrained dispatchable generation options and prevented flexible capacity from absorbing the excess wind output, exacerbating downward price pressure.
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.