Abstract: The invention relates to a method of thermo-chemical energy storage by carrying out reversible chemical reactions for storing heat energy in the form of chemical energy in one or more ammine complexes of transition metal salts of the formula [Me(NH3)n]X, wherein Me is at least one transition metal ion and X is one or more counterions in an amount sufficient for charge equalization of the complex, by using the following chemical equilibrium: [Me(NH3)n]X+?HRMeX+nNH3, characterized in that said heat storage is performed by endothermic cleavage of the NH3 ligands from the ammine complex and/or that the heat release is performed by exothermic loading of the transition metal salt with the NH3 ligands in at least two steps at different temperatures.