An energy management system is applied to a vehicle having a first power source, a first converter, an electricity storage part, and a second power source. The energy management system has a second converter, a heat storage part, a mode switching part, and a controller. The mode switching part switches between a heat storage mode and a heat radiation mode. The heat storage part changes to a first phase in a solid state when a temperature of the heat storage part is lower than or equal to a phase transition temperature, and changes to a second phase in a solid state when a temperature of the heat storage part exceeds the phase transition temperature. The controller controls the operations of the second converter and the mode switching part based on at least one of an electricity storage condition of the electricity storage part and a conversion condition of the first converter.