Western Australia’s Largest Isolated Power Grid Transforms with Renewables
The power grid in Western Australia is undergoing a significant change, driven by an increase in renewable energy sources and battery storage solutions.
A decade ago, coal and gas accounted for a staggering 90 per cent of the South West Interconnected System (SWIS). However, recent figures from the first quarter of 2026 reveal that renewable energy now meets 46 per cent of the system’s demand.
The Unique SWIS Structure
The SWIS stands out as it is isolated from the rest of Australia’s power infrastructure, separated by 1,000 kilometres of desert and spanning an area of 261,000 square kilometres, earning the title of the world’s “largest isolated grid”.
As Western Australia focuses on expanding its renewable energy capabilities, the grid-scale battery capacity for the SWIS has soared past 1 gigawatt (GW) over the past year. Moreover, the state has launched the Cheaper Home Batteries initiative, which has seen the installation of 50,000 batteries, amounting to 1.1 GWh of capacity, since its inception in July of last year.
Solar Power Growth in WA
In the second quarter of 2026, Western Australians collectively added 110 megawatts (MW) of rooftop solar capacity. To put this into perspective, Australia’s eight states and territories collectively installed 2.8GW (or 2800MW) of small-scale solar in 2025, with projections estimating an increase to 3–3.7GW in 2026.
On November 16 of last year, rooftop solar performance reached new heights, generating so much electricity that the demand for the SWIS dropped to an unprecedented low of 383MW—this figure is two-thirds lower than the previous record set six years earlier.
The Role of Battery Storage
This is where battery storage played a vital role. According to Kirsten Rose, executive general manager of AEMO in Western Australia, low demand periods can lead to instability in the grid due to fewer generators online to manage voltage and frequency, potentially resulting in power outages or equipment damage.
She noted that what once posed a significant operational challenge has now become manageable, thanks to grid-scale batteries that have begun charging and absorbing excess energy. This helps support demand and maintain grid stability.
Rose highlighted that the integration of grid-scale batteries has enhanced AEMO’s ability to handle times of low grid demand, which will be crucial for stabilising the SWIS during the spring and summer seasons.
Future Developments in Battery Storage
Looking ahead, a further 482MW of grid-scale battery storage is planned for construction across regional Western Australia as part of the Federal Government’s Capacity Investment Scheme. This development will provide even more resources for the SWIS to ensure stability and reduce dependence on costly coal or gas generation.
