In this work, thermodynamic properties including vapor–liquid equilibria, heat capacity, density and excess molar enthalpy of binary mixtures composed of {H2O + 1,3-dimethyl imidazolium methylsulfate, [DMIM][MeSO4]} and {H2O + 1-ethyl-3-methylimidazolium methylsulfate, [EMIM][MeSO4]} were measured at different temperatures and in a large range of composition. The thermodynamic properties were correlated using Non-Random Two Liquids (NRTL) model and different empirical correlations. The correlated values were significantly consistent with the experimental data. Then, experimental data were used to simulate the performance of absorption heat transformers using these two binary systems as working fluids. Simulation results show that binary systems containing alkylsufate based ionic liquids and water are adequately can be used for industrial absorption heat transformers even if they lead to slightly lower performances than aqueous lithium bromide solution.