NSW1 experienced sustained negative pricing at −$3.04/MWh across two consecutive intervals (20:55 and 21:00 on 18 September 2026), representing a minor severity event. Prices declined sharply from $64.31/MWh two intervals earlier, driven by a sharp influx of renewable generation into an already well-supplied market.
The generation mix at the time was dominated by wind (1531.91 MW) and solar (1307.86 MW), which together represented approximately 60% of total generation, whilst black coal (3455.33 MW) maintained baseload supply. The rapid price collapse from $22.72/MWh to negative territory suggests demand could not absorb the combined renewable output without constraint-driven curtailment. A binding constraint with marginal value of $89.82 (F_T+LREG_0050) indicates significant transmission or network limitations forcing expensive dispatch adjustments; the lower-valued binding constraints ($3.75–$3.99) suggest network relief mechanisms were activated but insufficient to prevent the negative excursion. The two-interval duration indicates a transient supply–demand imbalance rather than sustained oversupply.
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.