Tomago Battery Energy Storage System is a grid-connected energy storage project being developed by Australian integrated energy AGL Energy in New South Wales, Australia.
With a capacity of 500MW and four hours of storage (2,000MWh), it is designed to enhance reliability in the National Electricity Market (NEM) by providing firming capacity for renewable generation.
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The project will store energy from the electricity grid during low-peak periods and then scale up or down based on power needs.
It will support the state’s transition away from coal-fired generation while maintaining grid stability and operational resilience.
AGL took its final investment decision (FID) in July 2025, positioning the battery as a central element of its strategy to deliver 12GW of new renewable and firming capacity by 2035.
Project Location
The battery will be constructed within the Tomago Industrial Estate in the Hunter Region of New South Wales.
It is situated between the Pacific Highway and Old Punt Road, adjacent to the Tomago Aluminium smelter, Australia’s largest energy consumer.
The site provides strategic proximity to major demand centres and high-voltage transmission infrastructure. Its location allows integration into the NEM at a point where system strength and flexible capacity are increasingly important as legacy coal generation retires.
Financing and Ownership
AGL will finance the project directly from its operating cash flows and existing debt facilities, including green funding arrangements. Capital expenditure for the project is estimated at between A$800m and A$815m.
Tomago Battery Energy Storage System Capacity and Infrastructure
Tomago Battery Energy Storage System will deliver 500MW of power for up to four hours, equating to 2,000MWh of storage capacity. Planning consent sets this as the maximum energy storage threshold, providing scope for upgrades within the approved site boundaries.
Core infrastructure includes battery enclosures, inverters, transformers, switchgear, and grid connection facilities. The design enables participation in energy arbitrage, renewable firming, and frequency control ancillary services (FCAS).
Construction of the project will generate up to 200 jobs, with six ongoing operational roles once commissioned. The project is expected to have an operational life of 20 years.
Development and Timeline
The project achieved State Significant Development Consent on 8 November 2024, issued by the NSW Department of Planning, Housing and Infrastructure under SSD 57107216.
The consent sets environmental, transport, and community obligations, including a Voluntary Planning Agreement (VPA) worth approximately A$2.2m with Port Stephens Council.
Construction is scheduled to begin in October 2025, with commissioning targeted for September 2027.
Key development stages include site preparation, civil works, installation of Fluence’s storage system, commissioning, and market registration with the Australian Energy Market Operator (AEMO).
Tomago Battery Energy Storage System Technological Details
The battery will be delivered using Fluence’s Gridstack technology, designed for large-scale, long-duration storage.
The modular system is engineered for scalability, safety, and efficient thermal management. It incorporates advanced lithium-ion battery cells, digital controls, and inverters capable of providing grid-forming services.
The system will be supported by Fluence’s Mosaic platform, which integrates with AGL’s dispatch operations to enable optimisation across multiple markets.
The project’s development consent requires compliance with detailed environmental and operational standards, including noise, air quality, and waste management controls.
Power Purchase Agreements
Tomago Battery Energy Storage System will indirectly support Tomago Aluminium by enhancing regional reliability, though no contractual power purchase agreement (PPA) has been announced. The absence of a PPA indicates reliance on merchant market revenue, a common feature of large-scale batteries in the Australian NEM.
Contractors and Suppliers
Fluence has been appointed as the engineering, procurement, and construction (EPC) contractor. Fluence will provide its Gridstack energy storage technology, with the system designed to operate at 500MW /2,000MWh. The company will also deploy its AI-enabled Mosaic platform to optimise dispatch in the NEM.
