WA1 experienced a moderate price spike to $261.79/MWh in a single trading interval at 18:35 on 22 September 2026, representing an 81% increase from the prior interval's $144.82/MWh. Prices had been relatively stable in the $134–145/MWh range in the preceding 25 minutes before this sharp single-interval elevation.
The price spike was driven by binding constraints with material marginal values, with constraint F_TASCAP_RREG_0220 contributing 7.79 and 4.68 $/MWh and constraint F_T+RREG_0050 contributing 3.99 $/MWh across multiple instances, collectively accounting for approximately $24 of the spike elevation. The generation mix at the time shows substantial reliance on gas-fired generation (OCGT 454.66 MW and CCGT 300.68 MW) and battery discharge (408.47 MW), suggesting potential supply-side tightness or reserve adequacy constraints that binding constraint equations were designed to manage.
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.