Abstract Electrical energy storage (EES) has the potential to enable a transition to clean energy in the future as it brings flexibility into the electricity network. Uncertainties exist around EES regarding technology, costs, business models and market structures but experts agree on EES being beneficial. This study offers an economic analysis of the role of EES in low-carbon electricity supply. A GIS-supported hourly simulation study of Australia assesses the impact of adding EES to wind and solar generation on levelised cost of electricity (LCOE), installed capacity, generation mix and energy spillage. The study finds that EES deployment is able to lower LCOE in scenarios with high penetration of renewable sources. In the case study of Australia, it is found that EES between 90 and 180 GWh capacity can be economic for cost levels below 1,000 AU$ kWh−1. In addition, the study finds that EES can reduce LCOE by 13–22%, reduce installed capacity by up to 22%, and reduce spilled energy by up to 76%. It is shown that the generation mix is highly influenced by the magnitude of EES deployed.