Energy storage can facilitate the transition process from the actual energetic model to a model based on renewable energies. A lot of attention has been put in such technology, being the use of phase change materials (PCM) of high interest. However, design methodologies for PCM storage systems are still a limiting factor for its deployment. This paper compiles and structures the most common and promising design methodologies and highlights their usefulness and limitations. These methodologies are classified in six types: (1) empirical correlations and characterizing parameters, (2) dimensional analysis and correlations, (3) effectiveness–NTU, (4) Log Mean Temperature Difference (LMTD), (5) Conduction Transfer Functions (CTF), and (6) numerical models. Dimensionless correlations and effectiveness–NTU are the most common and straight-forward methods as well as the ones that offer more possibilities for general solutions. Empirical correlations and numerical models are problem based and difficult to generalize. On the other hand, the adaptation of LMTD and CTF to PCM systems still requires detailed research.