Carbon Forecast: Thursday 21 May 2026

NEM-wide carbon intensity at 06:30 AEST sits at sharply divergent levels across regions. Tasmania runs at 0.00 tCO2/MWh with 100% renewable penetration, driven entirely by hydro and a small wind contribution. South Australia is the next cleanest at 0.23 tCO2/MWh with 57% renewables — wind at 756 MW dominates the SA mix, supplemented by gas CCGT and OCGT balancing. NSW and Queensland are closely matched at 0.64 tCO2/MWh and 0.63 tCO2/MWh respectively, both with renewable penetration in the 27–28% range. Black coal accounts for the dominant share in both states — 5,631 MW in NSW and 4,714 MW in Queensland. Victoria is the highest-intensity region on the NEM at 1.01 tCO2/MWh with renewables at only 13%, where brown coal at 4,612 MW anchors the dispatch stack and gas OCGT at 558 MW provides additional output.

The overnight data reveals the pattern that will shape today's green windows. SA reached its lowest intensity between 18:00 and 21:30 AEST last night — touching 0.17 tCO2/MWh with renewables above 69% — driven by strong wind generation through the evening. NSW traced a clear trough between midnight and 06:00 AEST, where intensity fell to around 0.43 tCO2/MWh and renewables crept above 50%, with hydro at 1,178 MW and wind at 692 MW providing the bulk of low-emission output during the low-demand overnight period. Queensland's overnight renewable penetration ran at 43–47%, producing intensity readings in the 0.46–0.50 tCO2/MWh range, before morning demand ramp lifted coal dispatch and pushed intensity back above 0.70 tCO2/MWh. Victoria showed no meaningful overnight improvement, remaining above 0.94 tCO2/MWh throughout, reflecting the baseload profile of brown coal.

For today's outlook, the key dynamic is the absence of solar contribution — it is mid-May, pre-dawn at the time of this briefing, and the overnight generation mix is essentially what the morning peak will inherit. Solar output is negligible across all regions at this hour (NSW 145 MW, QLD effectively zero, VIC and SA at zero), so intensity will be driven by wind and hydro until demand ramps through the morning. In NSW, the intensity spike seen yesterday between 07:00 and 17:00 AEST — peaking at 0.67 tCO2/MWh — is the likely trajectory again today as coal lifts to meet the morning peak and solar remains subdued in winter conditions. Queensland intensity is expected to remain elevated at 0.63–0.75 tCO2/MWh through the bulk of the business day, with coal and gas OCGT carrying the load.

For carbon-sensitive scheduling, SA continues to offer the most accessible low-intensity windows on the NEM today — the wind resource is well established and the 57% renewable penetration at this hour is likely to persist or improve through the afternoon depending on wind conditions. Late evening from approximately 18:00–22:00 AEST is SA's structural low-intensity window based on the overnight trend. In NSW, the lowest-intensity periods are concentrated in the