Expected to be online in 2025, the battery energy storage system will cost between $300 million and $400 million and could hold enough energy to power one-third of Canberra for two hours during peak demand. This stored energy will be used to support our electricity grid. The Australian Capital. The ACT Government is future-proofing Canberra's energy supply by expanding its renewable energy storage with a new partnership with global specialist energy storage business, Eku Energy, launched by Macquarie's Green Investment Group.