Australia: Williamsdale Battery Starts Operation at 500 MWh

Eku Energy and the Australian Capital Territory Government commissioned the Williamsdale battery south of Canberra on November 5, bringing the 250 MW/500 MWh facility into operation and completing the utility-scale component of the territory’s Big Canberra Battery program.

The two-hour system contains 136 Tesla Megapack 2 units and can discharge enough power to cover the equivalent of up to one-third of Canberra’s electricity demand for two hours during peak periods, according to the ACT Government’s joint commissioning announcement .

Williamsdale battery moves from contract to operation

The November commissioning is a material change in project status. The ACT selected Eku Energy for the battery in 2023 , and Eku reached financial close in November 2024. The company now describes the Williamsdale BESS as commissioned and ready to support the ACT electricity network.

Eku Energy’s commissioning release identifies Consolidated Power Projects as the balance-of-plant contractor, Evoenergy as the distribution network service provider and the Australian Energy Market Operator as a participant in the grid-connection approval process.

The operational milestone arrived later than the schedule initially presented by the ACT Government. Its April 2023 announcement anticipated completion in 2025, while later project updates shifted the target into 2026. ABC News independently reported that the project timeline moved twice before the battery came online.

That timing distinction matters in a market where project announcements, contracts, financial close, construction and commercial operation are often reported as though they were equivalent. Williamsdale has now crossed the operating threshold; proposed Australian projects such as the 102 MW Glenrowan battery still have financing and construction milestones ahead.

A 15-year revenue-sharing agreement underpins the project

The battery’s commercial structure combines fixed public support with shared market revenue. Under the 15-year agreement, the territory pays Eku Energy a quarterly support charge and receives 50% of net revenue from the facility’s participation in Australia’s National Electricity Market.

An ACT Legislative Assembly disclosure puts the nominal support charge at A$368,250,784 over the operating period, excluding goods and services tax and assuming consumer-price-index increases. The government said forecasts made when the contract was signed indicated its revenue share should exceed that amount in net-present-value terms.

That remains a forecast, not a guaranteed return. Battery revenue will depend on market prices, dispatch, availability, ancillary-services demand and operating costs over the contract term.

The support charge also should not be confused with the project’s construction cost. The ACT’s 2023 project announcement estimated capital expenditure at between A$300 million and A$400 million, while the A$368.25 million figure covers indexed support payments over 15 years.

Grid-forming capability adds system-services value

The Williamsdale system was designed to operate in grid-forming mode, allowing its inverters to establish voltage and frequency references rather than only following an existing grid waveform. Eku has also said the facility can provide system-strength services and fast-acting frequency control ancillary services.

Those capabilities make the project more than an energy-shifting asset. A grid-forming battery can help stabilize a power system with increasing inverter-based wind and solar generation, although the commissioning announcements do not publish measured performance data for Williamsdale’s grid-forming functions.

Australia is deploying the same control approach at other large storage developments. Microgrid Media previously reported that Supernode Stage 3 in Queensland will add 260 MW/1,216 MWh of grid-forming storage , but that project remains under development rather than in service.

Reliability claims now face an operating test

The ACT Government says the battery can respond to grid changes within milliseconds and strengthen reliability during high-demand periods. Its 500 MWh energy rating supports two hours of discharge at the full 250 MW power rating, but the frequently cited “one-third of Canberra” comparison is an illustrative peak-demand equivalence, not a promise that the battery will serve a fixed share of the city in every event.

The facility connects through 12 collector grids, each with 12 step-up transformers, and a main transformer weighing more than 180 tonnes. Eku Energy will continue managing the asset.

The broader Big Canberra Battery program also includes neighbourhood batteries in Dickson, Casey and Fadden. The ACT says the combined network is intended to support its 2045 net-zero target and help maintain a stable electricity supply as electrification increases demand.

The project has also directed A$1 million to community organisations and energy research. Eku allocated A$500,000 to nine local groups and another A$500,000 to the Australian National University’s Centre for Energy Systems.

Commercial operation gives the ACT and Eku a physical asset against which those claims can now be measured. The next evidence to watch is not another capacity announcement, but the Williamsdale battery ‘s availability, market revenue, grid-services performance and contribution during periods of system stress.