The paper reviews energy storage technologies and their applicability to the Australian National Electricity Market (NEM). The increasing gap between maximum and minimum operational demand is likely to continue as time-varying renewable generation penetration proceeds. Recent severe weather events find the NEM ancillary services market for frequency and voltage control becoming increasingly important as the mechanical system inertia of thermal power stations reduces with the retirement of coal-fired power stations. To maintain grid stability through innovative technologies involving various storage technologies with different response times and endurances, a review of existing storage technologies for short to medium-term storage (such as flywheels, batteries, and supercapacitors) reveals that hybrid systems with different power, energy density, and fast response capabilities will be part of the solution. Pumped Hydro Energy Storage, Compressed Air Energy Storage System, hydrogen fuel cells, and fast response peaking hydrogen-fuelled gas turbines were reviewed for long-term storage. Batteries and Supercapacitors are assessed to be the solution for the immediate net zero targets for 2030-2050. While many varieties of batteries exist, metal ion batteries will continue to dominate with particular interest growing toward sodium ion batteries. Current challenges as well as opportunities for future research are highlighted.