Australian energy company Origin Energy is set to begin construction of a large-scale battery at the Mortlake Power Station in southwest Victoria, entailing an investment of around $400m.

The proposed battery for the Mortlake Power Station will be designed to have a 300MW capacity and is expected to deliver up to 650MWh of output.

Expected to be commissioned late in 2026, the battery will provide firm renewables supply and maintain reliable power for customers, said Origin.

Mortlake Power Station is a large-scale gas-fired power station located in Victoria with a generation capacity of 566MW, powered by gas from the Otway Basin.

Origin CEO Frank Calabria said: “The Mortlake battery is another significant step in our ambition to lead the energy transition through cleaner energy and customer solutions.

“I am pleased to announce that contracts have been signed with global energy storage systems supplier Fluence and site preparation and civil works are expected to commence over the coming months.

“Origin’s strategy is to accelerate renewable energy and storage in our portfolio and we expect large-scale batteries and other storage technologies to play a vital role in Australia’s energy transition.”

The proposed battery project closely follows the company’s decision last year, on its first large-scale battery at Eraring, which is currently in the construction phase.

In April last year, Origin made a final investment decision (FID) on the first stage of battery at the Eraring Power Station, committing to around $600m investment.

The first stage of the project included the construction of a 460MW battery storage system that could dispatch power for two hours.

Origin has the option to increase the battery to 700MW and four hours dispatch in the future.

The company has executed agreements for the supply and construction of the Eraring battery, which is anticipated to come online in the final quarter of the 2025 calendar year.

Calabria added: “Today’s announcement follows our decision last year to approve Origin’s first large-scale battery at Eraring, which is currently under construction.

“With the proliferation of wind and solar farms, particularly in Victoria’s South West Renewable Energy Zone, the Mortlake battery will help keep the grid stable and support more renewable energy coming into the system as the market continues to decarbonise.”