 The standard amount of energy released from hydrolysis of ATP can be calculated from the changes in energy under non @-@ natural ( standard ) conditions , then correcting to biological concentrations . The net change in heat energy ( enthalpy ) at standard temperature and pressure of the decomposition of ATP into hydrated ADP and hydrated inorganic phosphate is − 30 @.@ 5 kJ / mol , with a change in free energy of 3 @.@ 4 kJ / mol . The energy released by cleaving either a phosphate ( Pi ) or pyrophosphate ( PPi ) unit from ATP at standard state of 1 M are : 
