Carbon Forecast: Thursday 17 September 2026

SA1 is running at 0.0585 tCO2/MWh with renewable penetration at 89.24%, the lowest carbon intensity in the NEM this morning, backed by 902 MW of wind and minimal gas (124 MW combined OCGT/CCGT). TAS1 sits at 0 tCO2/MWh with 100% renewable supply, entirely hydro and wind (1,067 MW hydro, 434 MW wind), a position it has held through most of the overnight period. At the other end, VIC1 carries the highest intensity at 0.7183 tCO2/MWh despite 41.12% renewable penetration right now, a reflection of 3,734 MW of brown coal still online alongside 2,377 MW of wind. NSW1 (0.6561 tCO2/MWh, 25.35% renewable) and QLD1 (0.6479 tCO2/MWh, 26.01% renewable) sit in between, both leaning on black coal at over 5,300 MW each.

The generation mix data show why intensity is diverging across regions. SA1 and TAS1 have negligible thermal generation right now, so their carbon figures track renewable output almost one-for-one. NSW1, VIC1 and QLD1 all carry baseload coal above 3,700 MW, which puts a floor under their intensity even when wind and solar are contributing solidly, as seen in VIC1's wind fleet output of 2,377 MW alongside its coal fleet.

Looking at the trajectory from yesterday's pattern, NSW1 and QLD1 both show a strong intensity dip through the early morning hours (00:00-05:00 AEST), when NSW1 fell as low as 0.38 tCO2/MWh with renewable penetration above 56%, before climbing sharply through the day as solar output faded relative to demand and coal ramped to fill the gap, peaking near 0.75 tCO2/MWh in the early evening. VIC1 followed a similar but more pronounced swing, troughing near 0.72 tCO2/MWh overnight and spiking above 1.0 tCO2/MWh around midday as renewable share fell to single digits. SA1 shows the most volatility, swinging between 0.03 and 0.44 tCO2/MWh depending on wind output, with clear low-carbon windows overnight and in the late afternoon/evening as wind picks up again.

For carbon-sensitive loads today, the best windows are overnight into early morning (00:00-05:00 AEST) for NSW1 and QLD1, and late afternoon into evening (17:00-20:30 AEST) for SA1 and VIC1, when wind generation typically strengthens and solar taper coincides with renewable increases rather than coal ramp-up. TAS1 remains the standout for continuous low-carbon supply, effectively at zero intensity through the entire period. Midday (11:00-15:00 AEST) is the period to avoid for flexible load in NSW1, VIC1 and QLD1, where intensity peaks as coal and gas cover the gap left by fading solar and lighter midday wind.