In this study, the influence of different basic raw materials from technical to laboratory grade on the maximum storage capacity of CaBr2.6H(2)O is investigated via differential scanning calorimetry (DSC). Five samples of CaBr2.6H(2)O are prepared from laboratory grade basic raw materials, 1 CaBr2.6H(2)O sample is prepared from grown CaBr2.6H(2)O crystals and 1 sample is prepared from a technical grade CaBr2 brine. To exclude differences in the maximum storage capacity due to deviations in the water content of the samples, the water content was adjusted for each sample until it matched the stoichiometrically correct water content of CaBr2.6H(2)O of 35.10 wt % within an interval of +/- 0.05 wt%. The CaBr2.6H(2)O sample obtained from the grown crystals serves as reference sample and presents a melting enthalpy of (143 +/- 1) J g(-1) and a maximum storage capacity of (166 1) J g(-1) in the temperature interval between 30 and 45 degrees C. The decrease in maximum storage capacity of the laboratory grade samples relative to the reference sample ranges between - 1% and - 18%. For the technical grade CaBr2.6H(2)O sample the decrease in maximum storage capacity is 45%. However, if considering a temperature interval between 25 and 40 C for the evaluation of the maximum storage capacity, the difference between reference and technical grade CaBr2.6H(2)O is noticeably reduced to - 18%. The considerable differences in maximum storage capacity for the CaBr2.6H(2)O samples from different grade basic raw materials were obtained via DSC measurements with a sample size typically orders of magnitude smaller than in potential applications. For the use of certain grade basic raw materials to prepare CaBr2.6H(2)O as phase change material (PCM) in view of an application, it should be checked, if the CaBr2.6H(2)O samples show a volume -dependent behaviour.