Methods, systems and computer readable code for controlling a defrost cycle of a refrigeration device are disclosed. According to some embodiments, a defrost command is issued to a defrost heater at a time determined at least in part by a total wasted energy parameter of the compressor for at least one time interval. In some embodiments, time interval includes a plurality of runtimes, and the total wasted energy parameter of a runtime is measured relative to a chosen reference runtime such as a minimum energy runtime after a defrost or an early runtime after a defrost. Optionally, a sequence of wasted energy parameters of the compressor for a sequence of time intervals is analyzed, and then a correction is performed on at least one wasted energy parameter.