Abstract: A method for improving the total production of useful energy in an energy utilization system of a thermal power engine (1) that is liquid-cooled and is used for the production of thermal energy as well as mechanical energy. In the energy utilization system, thermal energy is taken from the coolant of the engine cooling system. At least a part of the coolant from the engine is led to a vaporization space (5) where, either by lowering the pressure or by increasing the amount of thermal energy within that space (5), a part of the coolant is transformed to vapor. The vapor is used within the energy utilization system for energy transport and/or as a medium for recovering energy.