Carbon Forecast: Friday 18 September 2026

South Australia and Tasmania are the standout low-carbon regions this morning, sitting at 0.015 tCO2/MWh (96.9% renewable) and 0.0 tCO2/MWh (100% renewable) respectively. SA's grid is running almost entirely on 1,336 MW of wind, while Tasmania is fully covered by 239 MW hydro and 427 MW wind. Queensland sits at the opposite end at 0.757 tCO2/MWh with renewable penetration down at 13.5%, reflecting 4,778 MW of black coal against just 354 MW wind and 211 MW solar as the evening solar ramp-down bites. NSW (0.593 tCO2/MWh, 32.5% renewable) and Victoria (0.467 tCO2/MWh, 61.7% renewable) fall in between, with NSW's 4,216 MW black coal fleet dominating and Victoria's 2,073 MW brown coal offset by a strong 3,305 MW wind contribution.

The mix driving these numbers is squarely about the solar-to-evening transition. Through the day, NSW and QLD both traced a clear intensity trough around midday-to-early-afternoon on the previous cycle — NSW dropped as low as 0.26-0.30 tCO2/MWh in the small hours when wind ran hard, before climbing back above 0.6 tCO2/MWh through the evening peak as coal and gas fill the gap left by fading solar. QLD's pattern is starker: intensity climbed steadily from 0.42 tCO2/MWh near midday to over 0.83 tCO2/MWh by 18:30 AEST as renewable share collapsed from above 50% to under 6%, driven by the loss of rooftop and utility solar output with minimal wind to compensate. SA and TAS show far less daily variation, holding sub-0.05 tCO2/MWh for most of the afternoon and evening on strong wind supply.

For the rest of today, expect NSW and QLD intensity to remain elevated through the overnight peak before easing again after midnight as wind generation typically strengthens and demand tapers — historical intervals show NSW falling from above 0.6 tCO2/MWh at 20:00 AEST toward 0.3-0.4 tCO2/MWh by the early hours. VIC should track a similar but shallower path given its larger wind base. SA and TAS are likely to stay in deep green territory (sub-0.05 tCO2/MWh) continuously provided wind output holds, making both regions the reliable low-carbon windows for flexible or carbon-sensitive load right now.

For carbon-sensitive scheduling, SA and TAS offer near-zero intensity windows essentially around the clock today. In NSW and QLD, the best windows for shifting load sit in the overnight-to-pre-dawn period (roughly 00:00–06:00 AEST), when wind contribution typically peaks and coal/gas backfill eases — avoid the current evening peak window (17:00–21:00 AEST) in both regions, where intensity is running near its daily high.