Ionic liquids are ideal absorbents for vapour absorption refrigeration systems because of their low volatility, and good solubility with different natural refrigerants such as ammonia, water, carbon dioxide, etc. However, the high circulation ratio and viscosity of ionic liquids pose many problems such as high pumping power and low absorber efficiency. One possibility is to use water as a cosolvent to overcome these drawbacks. The results of our study on the performance of a vapour absorption refrigerator operating with ammonia as the refrigerant and different ionic liquids and water as solvent and co-solvent respectively are presented in this paper. The results show that the use of water as a co-solvent results in a large decrease in circulation ratio, and hence the size of equipment, while the coefficient of performance decreases slightly. © 2014 Elsevier Ltd. All rights reserved.