Metal Foam-enhanced Cascaded Thermal Energy Storage (MF-CTES) has been proposed to solve the problem of poor heat transfer during heat exchange process, which is caused by unavoidable decrease of temperature differences. This paper conducts a theoretical study examining the overall thermal performance of Single-stage Thermal Energy Storage (STES), Cascaded Thermal Energy Storage (CTES) and MF-CTES, with both heat exchange rate and exergy efficiency being considered. The main findings are: heat exchange rate of STES is improved by CTES (up to 30%), and is further improved by MF-CTES (by 2-7 times); exergy efficiency of STES cannot be significantly improved by CTES (-15% to +30%), nor by MF-CTES; exergy transfer rate of STES is increased by CTES (up to 23%), and is further increased by MF-CTES (by 2-7 times). (c) 2012 Elsevier Ltd. All rights reserved.