The thermal energy required for CO2 recovery in chemical absorption plants results from three basic chemical properties; the reaction heat Of CO2 removal, the vapor-liquid equilibrium, and the CO2 and absorbent reaction rate constant. These properties are each independent from one another, making it difficult to predict the thermal energy that provides the total capability to recover CO2. A mathematical formula for predicting the thermal energy was made by calculating three factors; the heat of reaction of absorbent with CO2, the effective CO2 loading of vapor-liquid equilibrium data, and the degree of CO2 removal calculated from the reaction rate constant. The calculated thermal energy corresponded well with measured data from the Osaka Nanko CO2 recovery plant. This result indicates that this method for estimating the thermal energy required for CO2 recovery is useful for predicting the abilities of new absorbents.