Commodity Demand — SA1: Tuesday 18 August 2026
South Australia's spot price sits at -$4.24/MWh at 06:30 AEST with demand at 1,412 MW, extending a negative pricing stretch that has held since roughly 16:00 yesterday afternoon. Wind generation of 1,159 MW is comfortably covering demand and then some, pushing 93.4% renewable penetration and a carbon intensity of just 0.0323 tCO2/MWh. This overnight-into-morning negative price band reflects the now-familiar pattern in SA: strong wind output outstripping moderate demand produces sustained sub-zero pricing, with the trough intensity around -8/MWh overnight before recovering.
The demand trajectory today follows the standard shape: overnight lows near 900-1,000 MW (04:00-05:00 AEST) climbing through a morning ramp to a shoulder peak around 1,780-1,820 MW near 09:00-09:30 AEST, easing slightly through midday, then a second evening peak later in the day. Price sensitivity to demand is pronounced at the margins — every 100-200 MW swing in demand near the 1,700-1,800 MW band has recently triggered price moves of $20-30/MWh, visible in yesterday's data where demand climbing from 1,600 MW to 1,800 MW pushed prices from single digits to the $30-50/MWh range as wind output was insufficient to cover the ramp without dispatchable backup.
The forecast trajectory for the remainder of today points to a sharp price escalation from late morning: AEMO's forward curve shows prices lifting from -$1/MWh at 07:00 AEST to $80/MWh by 08:00, spiking to a forecast peak of $189/MWh around 10:00 AEST, before moderating to the $80-101/MWh band through midday and afternoon trading. This coincides with the demand ramp into the morning peak and reduced wind potential forecast for today (average wind potential just 8.5%, well down from recent days), meaning gas plant (currently just 83 MW from CCGT) will need to lift output materially to meet the shortfall as wind eases.
Two active AEMO market notices are directly relevant to today's supply-demand balance. AEMO issued a direction to AGL's Torrens Island B2 unit to synchronise and follow dispatch targets from 00:00 AEST today through to 15:00 AEST, citing inadequate synchronous generation for voltage control in SA — a reminder that thin synchronous capacity during high-wind, low-demand periods requires active intervention regardless of price signals. This voltage-driven direction, combined with the forecast wind potential drop-off, points to tighter dispatchable margins and supports the sharp forecast price escalation into the late-morning peak. Traders should watch the 08:00-11:00 AEST window closely, where forecast prices of $80-189/MWh represent the most material risk period today.