Thermal energy storages which store energy as heat, can compensate energy imbalance between heat generation and consumption. Several types of ice storage systems are applied to heating, ventilating, and air conditioning systems. In this paper, experiments on ice-on-coil and dynamic type are reported to examine thermal characteristics of tanks according to dimensionless response of outlet temperature. Efficiencies of the tank are discussed with respect to dimensionless response, response in a system and volumetric consideration of the tank. For the ice-on-coil type, the Archimedes number at inlet and the inlet enthalpy flow rate are the dominant parameters. Large Archimedes number and intermediate enthalpy flow rate result in lower outlet temperatures. For the dynamic type, as the mechanism of heat transfer is slightly different from the ice-on-coil type, higher velocity of inlet water maintains a lower outlet temperature. From the experimental results, simulation models for both types were developed. Simulations were conducted to estimate the volumetric efficiency under various conditions, considering actual applications. Eight factors were selected as design conditions. The relations among these factors and their potential effects on the thermal characteristics and the volumetric efficiency were derived by system simulations. The significance of the factors on the system was quantified and different effects on ice-on-coil and dynamic ice storage systems were found. Estimation tables to determine volumetric efficiency from the significant factors are presented. Copyright (C) 2007 John Wiley & Sons, Ltd.