Hysteresis in hydrogen storing materials during the hydriding-dehydriding cycles presents an efficiency loss which is to be minimized in order to get high performance. In this paper a new approach is presented for dealing with the hysteresis phenomena. Thus, the hydride systems TiFe0.9Mn0.1-H-2 and TiFe0.8M0.2-H-2 were considered in a thermal hydriding-dehydriding process performed at constant volume from room temperature up to 623 K and pressure ranging from 0.6 to 6.6 MPa. The obtained data were interpreted using a new mathematical approach aiming to optimize the hydriding-dehydriding path conditions in order to get minimum energy loss during their performance. It was found that optimum conditions are highly affected mainly by the applied starting pressure and the used hydriding-dehydriding temperature. The experimental results of the two substitutes were compared from the view point of energy loss due to hysteresis. It was found that Mn substitute is better in this respect. (C) 2004 Published by Elsevier Ltd on behalf of the International Association for Hydrogen Energy.