September introduces some of the mildest conditions of the year. Over the last five years, electricity demand has declined on average by about 6% from August with total renewable generation increasing by just over 9%, driven heavily by rooftop solar. Coal generation often sees sharp declines in September, and 2026 was a standout. Coal generation fell by 2,192GWh – more than 20% of the August total – the largest month-on-month decline since the NEM began.

Renewable generation in September is typically considerably lower than in the Summer months. However, with capacity added throughout the year and less frequent strong conditions, September can still produce new instantaneous and daily generation records, alongside very low levels of fossil fuel generation.

The NEM set a new instantaneous solar generation record on 18 September, reaching 24,020 MW and surpassing the previous record of 23,853 MW set on 9 December 2025. This was the first new NEM-wide solar record of 2026, and an unusually early point in the spring for one to occur. The last time an instantaneous solar generation record was set in September was 2021.

Solar generation - and rooftop solar in particular - varies significantly by season in the southern states. As a result, records set this early in spring tend to rely more heavily on strong Queensland output, where seasonal variation is less pronounced.

Our most recent record was no exception. Compared with the previous December record, the largest increases came from rooftop solar in NSW and Queensland. Utility-scale solar in both states could also have contributed more strongly, but output was constrained by substantial curtailment.

Victoria was the only state to record an increase in utility-scale solar generation, reflecting rapid recent capacity growth: 480 MW of the state’s 1,750 MW of utility-scale solar capacity has commenced operation in the past year.

South Australia set a new daily battery discharge record on 6 September, reaching 2,465 MWh - 7% above the previous record of 2,296 MWh set on 26 June. Battery discharge records in South Australia are typically associated with stronger output during the morning period. Looking at the 20 highest-discharge days over the past year, morning battery discharge was around 122% above average, while evening discharge at just 57% above average.

The 6 September record was a particularly striking example. Strong wind generation the previous day was followed by much weaker wind output the next morning, creating an opportunity for batteries to discharge heavily into the morning period.

Notably, several of South Australia’s largest batteries made little or no contribution to the record. Summerfield, the state’s largest battery, was still progressing through commissioning, while Templers BESS had only recently returned to the grid under ZEBRE’s operation. The record was therefore driven by unusually high cycling from existing operating facilities, led by Mannum, which discharged energy equivalent to 1.89 times its total storage capacity over the day.

The NEM recorded its lowest monthly fossil fuel generation on record in September, at 8,762 GWh - slightly below the previous low of 8,823 GWh set in November 2025. Both coal and gas generation are typically low in spring, although coal output more consistently falls in September, partly because it is a 30-day month, while gas generation is more variable.

September 2026 did not set a new record low for either fuel individually: the lowest monthly coal generation remains September 2025, while the lowest gas generation was recorded in April 2026. But with both running at low levels simultaneously, their combined output was enough to establish a new fossil fuel generation low.

The record was driven primarily by Queensland, which also recorded its lowest monthly fossil fuel generation in more than 26 years of NEM history. Queensland was in fact the only NEM region to record lower fossil fuel generation than during the previous NEM-wide record in November 2025.

Victoria recorded its lowest daily coal generation on 20 September, at just 44,071 MWh - 3% below the previous low of 45,414 MWh set on 16 January this year. Spring, with high renewable generation and relatively modest demand, is typically a period of planned coal outages, particularly in Victoria.

On 20 September, Victoria recorded its lowest demand of the month alongside strong wind generation. As a result, curtailed renewable energy exceeded total fossil fuel generation over a day in the state for only the second time on record, following the first instance in October 2025.

This record came despite a broader rise in Victorian electricity demand. Demand is increasing particularly quickly in Victoria, at almost 5% year-on-year, compared with around 2% across the NEM overall (possibly due to higher data centre demand, industrial load and/or the ongoing electrification of heating). That growth has generally pushed Victorian coal generation above September 2025 levels, a pattern not shared across all regions. Queensland, for example, recorded its lowest monthly coal generation since 1999.

The Branduda Energy Reserve reached FID on September 17. The 400 MW / 1,886 MWh battery will be the largest committed battery in Victoria, both by power capacity and energy storage. Construction is expected to begin in November, with the project scheduled to commence operations in late 2028. It will also be Birdwood Energy’s first battery in the NEM.

The Mortlake Renewable Hub has also reached FID. The hybrid facility combines a 435 MW solar farm with a 300 MW / 1,350 MWh battery capable of 4.5 hours of storage. Construction is also expected to commence in November, with operations targeted for early 2029.

The Merredin BESS commenced operations in late September, with output first recorded on 29 September. It is Atmos Renewables’ first operational battery in Australia. The company currently has no other batteries under construction, with two additional projects in development.

Merredin is the second new battery to begin operating in the WEM this year, with a further two projects currently under construction.

The Kondinin Wind Farm has reached financial close. Stage one of the project will add 130 MW of wind capacity, bringing the total under construction in WA to 625 MW, alongside 1,106 MW currently operating.

The facility is owned by Foresight Group, with 100% of its generation contracted to Synergy for the first seven years of operation. Synergy is Western Australia’s state-owned electricity generator and retailer.

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See all records and the latest facilities updates at Open Electricity.

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