NSW1 experienced brief negative pricing during the early morning of 31 May 2026, with spot prices reaching -$1.48/MWh in a single interval and sustaining around -$1.20/MWh. This minor event occurred across two intervals during an off-peak period characterised by high renewable generation (3,686 MW of wind and solar combined).
The negative pricing was driven by excess renewable generation during low-demand night-time hours, with wind and solar together contributing over 60% of the generation mix whilst synchronous coal generation remained inflexible at 2,849 MW. The binding transmission constraint (F_T+RREG_0050) with a marginal value of $5.44 suggests localised congestion prevented adequate export of excess supply, forcing the market into price suppression to manage oversupply within the region.
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.