This standard specifies the heat storage performance (thermal retention performance, Test methods for hot water tapping performance, heat exchange performance) are specified. However, this does not apply to heat storage tanks that use heat collection media or heat storage media that utilize latent heat. The term "thermal storage tank" as used herein refers to a heat storage tank with a capacity of 1000 L or less, including for hot water supply and heat storage, and includes those in which an auxiliary heat source device is integrated into the heat storage tank.