Electrical motors and drives are the driving force in industry and economy. Continuous improvement of their efficiency is critical to reduce CO₂ emissions; however, accurate measurement of their power losses poses a particular challenge. At present, it relies on input-output methods to test permanent magnetic (PM) machine drives and power electronics, which proved to lack precision for highly efficient ones. This problem is prevalent and insurmountable to employ high-precision measuring instruments alone. On the other hand, calorimetry offers a means of the thermal measurement of losses and thus removes the inherent inaccuracy in input-output methods. Furthermore, their measurement accuracy is independent of the power rating, efficiency, supply distortions or phase shifts of the device under test (DUT). In this work, design, analysis and testing of the shunt calorimeter will be investigated.