A method of automatically detecting an anomalous condition relative to a nominal operating condition in a vapor compression system (300, 1100), the method being characterized by: automatically calculating a measured input power function that includes a current measured from a compressor unit of the vapor compression system (300, 1100), which includes a condenser unit coupled to the compressor unit; receiving a condenser temperature indicative of an intake temperature from an air flow intake area of the condenser unit; receiving an interior temperature indicative of an indoor temperature of an indoor environment or a temperature of a closed managed thermal space within the indoor environment, wherein the interior temperature is a supply temperature from a supply output area of an evaporator unit in the vapor compression system (300, 1100); automatically calculating an expected input power function that includes the condenser temperature and the supply temperature, wherein the expected input power function is calculated independent of any pressure measurement relating to the vapour compression system (300,1100), and wherein the expected input power function includes a hyperplane, the hyperplane including a power offset constant, a first condenser temperature coefficient, and a second interior temperature coefficient, the power offset constant being expressed in the unit of the measured input power function, the first condenser temperature coefficient representing temperature sensitivity relating to the condenser temperature, and the second interior temperature coefficient representing temperature sensitivity relating to the return temperature, the first condenser temperature coefficient being multiplied by the condenser temperature in the hyperplane, the second interior temperature coefficient being multiplied by the return temperature in the hyperplane; responsive to the expected input power function deviating from the measured input power function by more than a predetermined tolerance, storing an indication that an anomalous condition exists in the vapor compression system (300, 1100). automatically calculating a measured input power function that includes a current measured from a compressor unit of the vapor compression system (300, 1100), which includes a condenser unit coupled to the compressor unit; receiving a condenser temperature indicative of an intake temperature from an air flow intake area of the condenser unit; receiving an interior temperature indicative of an indoor temperature of an indoor environment or a temperature of a closed managed thermal space within the indoor environment, wherein the interior temperature is a supply temperature from a supply output area of an evaporator unit in the vapor compression system (300, 1100); automatically calculating an expected input power function that includes the condenser temperature and the supply temperature, wherein the expected input power function is calculated independent of any pressure measurement relating to the vapour compression system (300,1100), and wherein the expected input power function includes a hyperplane, the hyperplane including a power offset constant, a first condenser temperature coefficient, and a second interior temperature coefficient, the power offset constant being expressed in the unit of the measured input power function, the first condenser temperature coefficient representing temperature sensitivity relating to the condenser temperature, and the second interior temperature coefficient representing temperature sensitivity relating to the return temperature, the first condenser temperature coefficient being multiplied by the condenser temperature in the hyperplane, the second interior temperature coefficient being multiplied by the return temperature in the hyperplane; responsive to the expected input power function deviating from the measured input power function by more than a predetermined tolerance, storing an indication that an anomalous condition exists in the vapor compression system (300, 1100).