In this paper, both the energy and efficiency analyses of the coil energy recovery loop system for various operating conditions were performed. A coil energy recovery loop system operates for sensible heat recovery only, with seasonally reversible energy transfer. It consists of two finned tube air-to-water heat exchangers, placed in the supply and exhaust air streams and connected in a closed loop via counterflow piping through which an intermediate heat transfer fluid (typically water or freeze-preventive solution) is pumped. For the purpose of analysis, the original simulation model of the system was developed. This model enables the analysis of the system operation, together with monitoring of both use and recovery of heating or cooling energy, electricity consumption of the electrical appliances, and also determination of the system efficiency value for various operating conditions in the unsaturated area of moist air. It is also possible to integrate this model in the simulation model of a complex air-conditioning system. Besides the simulation model developed, the extensive measurements on the coil energy recovery loop system with 12 tube rows in the flow direction were performed to determine heating, i.e. cooling capacity in different operating points. For this purpose, the experimental rig was designed and installed in order to conduct the measurements on the system in its true dimensions, placed in the air-conditioning unit. Based on the measurement results, the system efficiencies were determined for the measured set of operating points. With the developed simulation model of the coil energy recovery loop system, consistent and stable results were obtained, and their reliability was proven by comparison with the measurement results. The differences between the simulation and measurement results were in the range of +/- 3%. The influences of the air streams volumes, the air streams velocities, the water flow mass and the operation seasons on the system efficiency were presented in the diagrams. The obtained results are the base for forming the set of parametric curves for determining the system characteristics at diverse operating points. Copyright (C) 2003 John Wiley Sons, Ltd.