In large latent heat storages based with the phase change material (PCM) being a salt hydrate, it is difficult to assure the stoichiometrically correct hydrate concentration of the salt hydrate. In this study the impact of the concentration of CaBr2 + H2O in a concentration range of about 2.6 wt% around the congruent melting CaBr2 center dot 6H(2)O on the melting enthalpy and the maximum storage capacity is exemplary investigated via differential scanning calorimetry (DSC) and via a model. The melting enthalpy of CaBr2 center dot 6H(2)O is found to be 142.1 jg(-1), which is significantly larger than the value indicated in literature (115.5 j g(-1)). For a CaBr2 concentration around 0.8 wt% lower than the concentration of CaBr2 center dot 6H(2)O, adecrease of over 17% is found for both the melting enthalpy and the maximum storage capacity. A good agreement is found for the maximum storage capacity between the experimentally determined values and the values determined by the model. (C) 2015 Elsevier B.V. All rights reserved.