WA1 region experienced a moderate price spike to $252.50/MWh during the 23:10 trading interval on 21 July 2026, representing a 37% increase from the prior interval. Prices had been rising progressively from 22:45 onwards, with the spike occurring during evening peak demand when wind and solar generation were minimal.
The price spike was driven by binding constraints, primarily constraint NSA_Q_GSTONE34_250 which held a marginal value of $25.81/MWh—the largest contributor to dispatch costs in this interval. The generation mix at the time was heavily dependent on gas-fired generation (1,351 MW OCGT and 332 MW CCGT) and coal (622 MW), with renewable contributions limited to 112 MW combined wind and solar, forcing the market to rely on higher-cost peaking capacity. The binding constraint structure and tight supply conditions during evening demand suggest system limitations constrained the economic dispatch of lower-cost generation sources.
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.