Abstract In this work, two ionic liquids with a 1-hexadecyl-3-methylimidazolium cation were synthesized with different anions; chloride and saccharinate, respectively, both of them showing melting points above room temperature, ranging between (324.15 and 338.15) K and enthalpies of fusion close to or higher than 100 J/g, making them potentially suitable phase-change materials (PCMs) for latent heat storage. This application potential can be enhanced by a suitably large heat capacity and thermal conductivity of the material both in the liquid and solid phase. Heat capacity was therefore measured in this work as a function of temperature using the differential scanning calorimetry (DSC) to determine how it is affected by the anion structure. Care has been taken to evaluate the influence of the phase change on the measured data. The experimental data have then been analyzed by means of methods based on mathematical gnostics (MG). As a non-statistical approach towards data uncertainty, MG enabled us to analyze the underlying phenomena that affect the value of the experimental heat capacity.