State-of-the-art absorption chillers using conventional working pairs still suffer from problems like crystallization, corrosiveness, and a relatively low efficiency. To improve this technology, different working pairs as well as plant designs are investigated using the simulation tool AspenPlus. The simulation is validated by comparing the results of single-effect absorption chillers using the current commercially applied working pairs water/lithium bromide and ammonia/water with literature data. To increase the efficiency, double-effect absorption chillers are implemented and analyzed. The performance of two kinds of double-effect cycles, series and parallel, is compared using the working pair water/lithium bromide. In addition, ionic liquids (ILs) are investigated as a sorbent in order to improve the technology. So far, ILs have not been implemented in AspenPlus yet. Therefore, a guideline for the implementation of ILs in AspenPlus is outlined and the accordant phase equilibria results are validated with literature data. Simulations of single-effect cycles using the ILs 1,3-dimethylimidazolium dimethylphosphate ([MMIM][DMP]) and 1-ethyl-3-methylimidazolium dimethylphosphate ([EMIM][DMP]) in combination with water as a refrigerant are performed and the results are compared to conventional working pairs. It is shown that by using ILs, similar or even higher coefficients of performance (COPs) can be achieved in comparison to conventional working pairs. Moreover, the findings reveal that the main benefit of using ILs as a sorbent consists in providing a broader operating range with respect to heat source temperature.