Latent heat energy storage systems (LHESS) are one potential technology that can be used to store thermal energy when there is a mismatch between time of production and time of utilization of such energy. Design of LHESS requires knowledge of the heat transfer process within them, as well as the phase change behavior of the phase change material (PCM) use. COMSOL Multiphysics can be used to model (LHESS), enabling testing of a multitude of configurations, as well as an optimization of the geometry used. Natural convection plays a crucial role during the charging phase of the LHESS (melting of the PCM), and methods to incorporate this heat transfer mode within COMSOL simulation of PCM melting have been underway for quite some time. This paper presents a comparison between two such related methods, which are both treating the PCM as a liquid regardless of its actual phase; but are using added function to " solidify " this liquid when the PCM is below its melting temperature. Tests were conducted using COMSOL Multiphysics 4.3 and a simple 2D geometry is used to perform the comparison. Although the first method presented is intuitive and simple to increment, it was found that the second method is more robust, stable and has a better convergence.