Concerns over the continued use of fossil fuels in electricity generation and transport are stimulating the deployment of renewable energy technologies, and hybrid or fully electric vehicles. Utilizing energy storage that can cope with high power demands may assist with these applications. Supercapacitors can demonstrate high power densities and long cycle lives. Aqueous aluminium-ion (Al-ion) cells are a battery chemistry in development. Aqueous Al-ion cells can also operate at high charge/discharge rates and have demonstrated impressive cycle life. These similarities suggest they may compete with supercapacitors to address applications where these characteristics are desirable, such as assisting with power quality. This work presents a comparison of the technologies to assess their relative advantages and disadvantages.