Abstract: A method is described for the performance optimization of refrigeration devices fed with refrigerant, in particular of air refrigeration devices in which a setting value is formed for an electrically or electronically operatable expansion valve in dependence on different temperature measurements continually ensures the ideal filling of the vaporizer. The invention includes a method of optimising the performance of a fan air refrigerator and of determining the ideal timepoint for defrosting is described, with the time for defrosting being determined by a comparative monitoring of a temperature difference, on the one hand, and a time related monitoring of the refrigerant throughflow, on the other hand. In addition the cold room temperature is regulated by the supply air sensor by switching on and switching off the compressor.