NSW1 experienced two intervals of minor negative pricing at approximately $-0.55/MWh on 17 September 2026 at 22:05 and 22:30–22:35 UTC, with prices recovering to positive levels ($25–$43) in between. The negative pricing occurred within a generation mix dominated by solar (3476 MW) and black coal (2848 MW), supported by wind (218 MW) and battery (80 MW) output.
The negative pricing episodes appear driven by binding constraints on lower and raise regulation services (F_T+LREG_0050 with marginal value $12.70 and F_T+RREG_0050 with marginal value $3.73), which likely constrained dispatch flexibility and forced excess generation to be scheduled at negative rates. The high solar output combined with moderate daytime demand at the time created conditions where marginal generation could not be efficiently dispatched, resulting in temporary price suppression despite the overall generation mix remaining conventional-coal-heavy (approximately 7500 MW total supply).
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.