Australian utility giant Origin Energy has announced an AU$80 million (approximately US$53.4 million) investment to further expand Stage 4 of its Eraring battery storage project in New South Wales, bringing total capacity to 700 MW/3,160 MWh (3.16 GWh) and solidifying its position as Australia’s and the Southern Hemisphere’s largest battery energy storage system.
Four-Stage Expansion Creates Global Benchmark
The Eraring battery storage project is located at Origin Energy’s Eraring Power Station, Australia’s largest single-site coal-fired power plant with 2,880 MW capacity. The coal plant is scheduled to close in August 2027, though it may remain operational until 2029.
Stage 4 expansion will add 360 MWh of storage capacity to the existing 240 MW Stage 2, extending discharge duration from 4 hours to nearly 6 hours. Upon completion of all four stages, total capacity will reach 700 MW/3,160 MWh with an average storage duration of 4.5 hours, capable of powering over 150,000 households when cycled once daily.
Origin Energy Executive General Manager, Energy Supply and Operations, Greg Jarvis stated: “When complete, Australia’s largest power station site will host the nation’s largest approved battery storage system, reinforcing Eraring’s role as critical infrastructure at the center of Australia’s energy system.”
Wärtsilä Powers Technical Delivery
Finnish technology group Wärtsilä has been selected to deliver all four stages of the project. The company won Stage 1 in 2023, Stages 2 and 3 in 2024, and Stage 4 in Q4 2025. Stage 4 will utilize Wärtsilä’s Quantum energy storage system, featuring modular and compact characteristics.
Tamara de Gruyter, President of Wärtsilä Energy Storage, stated: “This extension marks another important milestone in Wärtsilä’s path towards enabling a secure, renewable energy future. Alongside Origin, we are setting a new global benchmark for large-scale energy storage.”
The project employs Wärtsilä’s GEMS Digital Energy Platform for management, specifically designed to manage complex GWh-scale projects like Eraring, optimizing performance, reliability, and value.
Supporting Grid Stability
The Eraring battery storage system connects to Australia’s National Electricity Market (NEM), providing critical grid services including frequency control, firming capacity, and system strength support, essential for enhancing system security and reliability.
Stages 2 and 4 batteries will be equipped with grid-forming advanced inverter technology, capable of providing Virtual Synchronous Machine functionality, including short circuit current capability, reactive current control, and synthetic inertia to support grid stability.
This expansion will help balance the grid as renewable generation grows and coal-fired plants retire. The battery system charges during daytime when solar and other renewables are abundant and discharges during evening peak demand, providing critical firming capacity.
Construction Progress and Impact
Stage 4 construction commenced in December 2025, with expected operation in Q1 2027. Stages 1 and 3 (combined 460 MW) are planned for early 2026 commissioning, while Stage 2 (240 MW/1,030 MWh) will come online in Q1 2027.
With Stage 4 underway, Wärtsilä’s energy storage portfolio in Australia now exceeds 5.8 GWh. Origin Energy has committed to developing or contracting a total of 1.7 GW of large-scale battery storage projects.
The Eraring project leverages existing transmission and grid connection infrastructure onsite, minimizing the need for long-distance transmission line construction, providing a successful template for Australia’s energy transition.
