Victoria’s second-largest big battery poised to charge up, next to the state’s biggest gas generator

Victoria’s second-largest big battery, which is nearing completion next to an existing gas plant in the state’s south-west, has joined the national grid management system ahead of final tests and commissioning.

Origin Energy’s 300 megawatt (MW) and 650 megawatt-hour Mortlake battery energy storage system (BESS) appeared on the Australian Energy Market Operator (AEMO) Market Management System (MMS) last week, according to Geoff Eldridge from Global Power Energy.

In a separate post, Eldridge says the Mortlake BESS has since shown the “first signs of active integration” in the National Electricity Market (NEM), including through “initial pulse testing” on Friday morning.

“These are standard ‘first-motion’ steps used to verify that the inverter controls and AEMO communication links are responding correctly before the battery scales up to its 300 MW operating maximum via the hold point testing,” Eldridge says here.

For Origin, the progress at Mortlake is just the latest BESS milestone it has chalked up in 2026.

In January, Origin marked the start of commercial operations of its 460 MW/1770 MWh stage 1 Eraring battery, in the shadow of the coal plant of the same name, in New South Wales.

And last month it announced the shift to full operations of the 260 MW, 619MWh stage one of Quinbrook’s Supernode battery, in Brisbane, with which Origin has a commercial tolling agreement.

The Mortlake BESS, with its storage volume of 650 MWh is currently the second-largest rated battery in Victoria, following the Melbourne Renewable Energy Hub (200 MW, 800 MWh).

The system has been registered on the AEMO MMS with a maximum operating capacity of 300 MW (440 MW registered capacity) and a maximum rate of change of 120 MW per minute. 

In comments made in mid-February, Origin’s general manager of energy supply and operations, Greg Jarvis, stressed the critical role the gentailer sees battery storage playing in supporting the energy transition.

“With Supernode Stage 2, along with our Eraring 2 and Mortlake batteries, coming online in the coming months, Origin’s battery storage portfolio will grow to 1.7 GW across owned and tolled large scale projects,” Jarvis said.

“It is not just about scale, but about placing storage at the right location in the network and delivering long term infrastructure assets that are purpose-built to support the next phase of power system evolution.”

The Mortlake BESS has been built next to Origin’s existing Mortlake power station, Victoria’s largest gas-fired generator, with a generation capacity of 566MW.

“A large-scale battery at Mortlake will help keep the grid stable and support more renewable energy coming into the system as the market continues to decarbonise,” Origin says on the project website.

“Mortlake’s existing links to transmission infrastructure and availability of suitably zoned land owned by Origin also make it an ideal location for a large-scale battery.”

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