Thermal energy storage tanks are widely used in different applications. There are many studies in the literature on increasing the efficiency of thermal storage tanks. Although air bubble injection systems were also used in different types of heat exchanger in the literature, no study has been detected about the effect of air bubble injection on the performance of thermal storage tanks. In this study, an air bubble injection system was integrated into a storage tank and the effect of bubble formation on heat transfer was experimentally examined. Experiments were conducted on the tank with and without air bubble injection. The results of the study showed that the tank with air bubble injection increased the amount of heat removal between the storage fluid and heat removal fluid by 11% and the amount of heat removal between the storage fluid and environment by 14%. The study also showed the overall heat transfer coefficient between the storage fluid and environment increased approximately fivefold and the overall heat transfer coefficient between the storage fluid and heat removal fluid increased approximately twofold.