Systems and methods for performing dynamic coefficient of performance calculations for refrigeration systems are provided. A controller calculates a weighted Carnot efficiency of a refrigeration case based on outdoor temperature data, refrigeration case temperature data, a case load of a refrigeration case, and a case defrost status of the refrigeration case. The controller calculates a weighted coefficient of performance based on based on a refrigerant type, the case load of the refrigeration case, the case defrost status of the refrigeration case, and at least one of the of the refrigeration case temperature data and pressure data. The controller calculates a system performance index (SPI) for the refrigeration case based on the weighted Carnot efficiency of the refrigeration case and weighted actual Carnot efficiency. The controller generates, in response to the SPI being below a threshold, an output indicating that the refrigeration case is operating below a threshold efficiency.