Carbon Forecast: Tuesday 15 September 2026

South Australia and Tasmania continue to anchor the low end of NEM carbon intensity, at 0.027 tCO2/MWh (94.5% renewables) and effectively 0.0 tCO2/MWh (100% renewables) respectively as of the latest 6:30am interval. Tasmanian hydro output of 1,050 MW plus 304 MW of wind is meeting the entire regional load, while SA's 1,429 MW of wind generation dominates its mix with negligible gas contribution (83 MW CCGT, near-zero OCGT). At the other end, Queensland sits at 0.721 tCO2/MWh with renewable penetration down to 17.7%, driven by 5,189 MW of black coal against just 413 MW wind and 212 MW solar. Victoria is close behind at 0.732 tCO2/MWh (40% renewable) with 3,638 MW of brown coal generation, while NSW sits mid-pack at 0.609 tCO2/MWh (30.7% renewable) on 5,178 MW black coal offset by 873 MW wind and 661 MW hydro.

The generation mix is the direct driver here: SA and TAS have effectively decoupled from thermal generation overnight, while NSW, VIC and QLD remain coal-anchored baseload regions where intensity tracks demand and solar availability. Overnight data shows a clear diurnal pattern — NSW intensity dropped as low as 0.341 tCO2/MWh around 4:30am AEST as wind output firmed and demand eased, before climbing steadily through the morning ramp as coal plants respond to rising load and solar hasn't yet reached peak output. QLD followed a similar but more pronounced pattern, bottoming near 0.424 tCO2/MWh overnight before climbing above 0.80 tCO2/MWh through yesterday's afternoon peak as renewable share fell to single digits.

For today, expect NSW and VIC intensity to ease modestly through mid-morning as solar ramps, with renewable penetration in NSW likely to push back toward 55-60% in the pre-dawn to early-morning window, mirroring yesterday's trough near 4:00-5:00am. QLD's lowest-intensity window typically falls overnight into early morning (historically dropping to the low 0.40s tCO2/MWh around 11pm-1am AEST) before deteriorating through the afternoon as coal dispatch dominates and renewable share compresses toward 8-15%. SA and TAS remain consistently low-carbon through the entire day regardless of time-of-day, making them the most reliable choice for carbon-sensitive load-shifting, while NSW and VIC offer the best green windows overnight and in shoulder periods (10pm-6am AEST) — traders and sustainability managers targeting minimum-emissions dispatch in the eastern mainland regions should prioritise those overnight hours rather than the afternoon peak.