The performance of a system for simultaneous air conditioning and domestic hot water heating is estimated numerically in this study. The system consists of air cycle refrigerator, desiccant rotor, evaporative cooler and heat recovery heat exchanger. The system uses air and water which are natural and safe substances. The system can supply air at low temperature and humidity. Also, it is easy to control the humidity of supply air by using evaporative cooling process before supplying air to the conditioning area. A recovery of exhausted heat from the desiccant rotor significantly decreasing not only the consumption of primary energy for heating domestic hot water but also the calefaction to the surroundings due to the rejection of heat. The system can supply hot water at a significant high temperature. The proposed system coefficient of performance is greater than the coefficient of performance of conventional system composed from vapor compression cycle and gas heater.