The use of by-products or wastes as phase change materials (PCM) in thermal energy storage (TES) systems is a good option to decrease the cost of such systems. One of the main disadvantages of PCM if inorganic materials are used is subcooling, as was found with bischofite, a by-product from the Chilean non-metallic industry, which subcooling is about 36 degrees C. Subcooling can be reduced by the addition of nucleating agents, but the selection of the best nucleating agent should be done taking into consideration the physical and chemical parameters of the salt hydrate. In this paper the parameters considered were the solubility of the materials in water, the chemical structure and the crystalline structure (crystal system, lattice parameters, density, cell volume, Z, and space group). It could be concluded that solubility, chemical structure and the crystal system have no influence in the nucleation capacity of a salt hydrate. The parameter that needs to be considered when selecting a nucleating agent for a salt hydrate is the lattice parameters of the crystal structure (cell longitude or angle). (C) 2016 Elsevier B.V. All rights reserved.