Hornsdale Power Reserve is a 150MW/194MWh grid-connected energy storage system co-located with the Hornsdale Wind Farm in the Mid North region of South Australia.
Between 2017 and 2020, it was the largest lithium-ion battery in the world.

During 2017 Tesla, Inc. won the contract and built the Hornsdale Power Reserve, for a capital cost of A$90 million, leading to the colloquial Tesla big battery name.In November 2019, Neoen confirmed that it was increasing capacity by a further 50MW/64.5MWh to a combined 185 MWh. The increased storage capacity was installed by March 23, 2020, and the increased power became operational in early September 2020.