Williamsdale BESS starts commercial operation in the ACT

By Grace Kim

A 200 MW/500 MWh battery on a 26-hectare site about 40 kilometres south of Canberra has entered commercial operation, becoming the Australian Capital Territory’s largest operating battery.

The Williamsdale battery energy storage system, or BESS, sits in Tuggeranong on the ACT-New South Wales border. Built by London-headquartered utility-scale storage developer Eku Energy, it anchors the Big Canberra Battery Project and provides capacity equivalent to one-third of Canberra’s electricity needs for two hours during peak demand.

Eku Energy Chief Operating Officer Tom Best said: “We thank our delivery partners for our commitment over the past nearly two years.” He described commissioning the Williamsdale BESS as a significant achievement.

What does 500 MWh change for Canberra’s peak demand?

The operating asset adds a two-hour peak-demand resource equivalent to one-third of Canberra’s electricity needs. That capacity belongs to the utility-scale Williamsdale installation, not the separate behind-the-meter batteries installed at ACT local government sites as part of the broader project.

The comparison defines the operating claim precisely: it covers one-third of the city’s demand at peak for that two-hour window, rather than Canberra’s full electricity requirement. Eku says the BESS will support the ACT electricity network and strengthen energy security and reliability in both the territory and NSW.

The project carries a stated cost of more than $300 million (US$210 million). Its commercial start moves Williamsdale from delivery into service, making sustained peak-period performance the next test for the territory’s largest battery.

Delivery and technology

The 26-hectare installation uses Tesla Megapack 2 XL batteries. Adelaide-based Consolidated Power Projects served as Eku Energy’s balance-of-plant contractor and delivered the project’s high-voltage electrical infrastructure.

The arrangement separates Eku’s developer role from CPP’s specialist electrical work. Together, their delivery brought the BESS into commercial service after the nearly two-year commitment period Best cited.

Community benefits and funding

From the project’s outset, the ACT government collaborated with Australian National University to conduct a workshop with community stakeholders that co-designed the Big Canberra Battery Project. The project combines a $500,000 grant for ANU’s Centre for Energy Systems with an equivalent $500,000 for nine local community projects.

Eku Energy funded the university grant to examine the role of utility-scale batteries and improve public understanding of their benefits and challenges. The Powering Big Dreams benefits-sharing program delivered the second $500,000 to nine projects with these named local beneficiaries:

• Southern ACT Catchment Group
• Fearless Women
• St Vincent de Paul Society
• Rise Above Cancer Relief
• YWCA Canberra
• The Stellar Company
• Australian River Restoration Centre
• OzHarvest
• Canberra Environment Centre

The grant and equivalent community allocation give the program two identifiable financial commitments: one for technical research and public understanding, the other for named local organizations. Each component can therefore be tracked against a stated amount and recipient.

Built capacity and the next test

The Big Canberra Battery Project comprises an operating 200 MW/500 MWh Williamsdale BESS and behind-the-meter batteries at nine ACT local government sites installed in 2024. A further two local-government batteries went in during 2025, bringing that installed group to 11.

The project record therefore separates an operating utility-scale asset from an installed behind-the-meter fleet. Commercial operation gives the ACT network a 500 MWh peak-period resource, while the 11 installed batteries extend the BCBP across ACT local-government sites.

Canberra aims to achieve net-zero emissions by 2045. The decisive next milestone is sustained peak-demand operation: the test is whether Williamsdale delivers the stated two-hour support for one-third of Canberra while maintaining the reliability benefit claimed for the ACT and NSW.