Research in the field of phase change materials (PCMs) requires that the temperature dependence of the thermal storage capacity be well known for the selection of PCMs as well as for simulation input. A differential scanning calorimeter (DSC) is often used, but it substantially misrepresents the true heat capacity in the vicinity of large-enthalpy phase transitions. Therefore, other suitable experimental techniques should be applied for the determination of the thermal storage capacity. Peltier-element-based adiabatic scanning calorimetry (pASC) measures the heat capacity and the enthalpy of PCMs in thermodynamic equilibrium, thus removing the rate dependence and deformation that are inherent to DSC. The technique is illustrated here by measurements on the pure alkane tricosane (C23), the commercial alkane mixture RT42 and its bound counterpart PX42.