WA1 experienced a significant price spike to $351.71/MWh in the 03:05 trading interval on 20 September 2026, representing a 157% increase from the $136.87/MWh seen in the preceding four intervals. The spike was isolated to a single five-minute trading period within the WEM.
The price spike was driven by binding constraints on regulation services, with constraint F_T+LREG_0050 displaying the highest marginal values ($49.97 and $35.79), indicating tight lower regulation capacity relative to system requirements. The generation mix of approximately 1,831 MW (dominated by wind at 756.59 MW and 567.12 MW contributions) combined with active thermal generation suggests a demand for downward regulation capacity during this pre-dawn period, with the binding constraint preventing adequate reserve deployment and driving the market price to the regulatory ceiling.
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.