A heat storage system without an evaporator promises high-density heat storage and a high rate of heat output since the solid-liquid product that is formed will itself be transferred as a heat medium to an object that requires heat. In this study, we compared the characteristics of this system using solid CaCl2, CaBr2, or LiBr with liquid H2O as reactants for the storage system. The exothermic heat produced for each reaction was measured and a relationship between the equivalence ratio and the reaction heat was observed. Heat values of 622, 534, and 481 kJ/L were obtained for CaBr2/H2O, LiBr2/H2O, and CaCl2/H2O, respectively. CaBr2 has the highest solubility and heat storage density of the three materials, as well as the highest heat value. The rate of heat output using CaBr2/H2O reached 10 kW/L 10s after the reaction was initiated, and thus CaBr2 is considered the most effective material for this system.