Western Australia’s power grid is undergoing a transformation underlined by a proliferation of renewable energy and battery storage.
While 10 years ago, 90 per cent of the South West Interconnected System – known as the SWIS – was powered by coal and gas, renewable energy supplied 46 per cent of SWIS demand in the first quarter of 2026.
The SWIS is unique. Separated from Australia’s main grid by 1000km of desert and covering 261,000 square kilometres, it’s been labelled the world’s “largest isolated grid”.
As WA prioritises renewable energy deployment, SWIS grid-scale battery capacity surpassed 1 gigawatt (GW) over the past year. The state has taken up the Cheaper Home Batteries challenge as well, with 50,000 batteries – or 1.1GWh of capacity – installed through the program since it was introduced July last year.
Western Australians also added 110 megawatts (MW) of rooftop solar in the second quarter of 2026. For context, 2.8GW – or 2800MW – of small-scale solar was installed across Australia’s eight states and territories in 2025, with expectations for 3–3.7GW to be installed in 2026.
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Rooftop solar outdid itself on November 16 last year, producing so much electricity that SWIS demand fell to a record low of 383MW – two-thirds lower than the previous record set six years ago.
Battery storage stepped in.
“During such low demand conditions there are fewer generators online to help manage system voltage and frequency, making the system less stable and potentially resulting in outages or damage,” AEMO executive general manager – Western Australia Kirsten Rose said during the WACCC WA–Asia Business Forum last week.
“What would once have been a significant operational challenge became largely a non-event, because grid-scale batteries began charging, absorbing excess energy, supporting demand and helping to keep the grid stable.”
Rose said grid-scale batteries have improved AEMO’s ability to manage periods of low grid demand, which will help buttress the SWIS during the spring and summer months.
And with a 482MW pipeline of grid-scale battery storage set to be built across regional WA under the Federal Government’s Capacity Investment Scheme, the SWIS will be able to call on even more resources to sought stability and limit the reliance on higher-cost coal or gas generation.