Abstract-A mathematical model is derived which allows to compute instantaneously the conduction and switching losses in two-level voltage source inverters (2L-VSIs) regardless of the employed modulation scheme. The model is based on the use of switching vectors applied to the considered VSI, taking into account the instantaneous conduction and switching losses of the semiconductor devices. The advantages of this method are, (i) it can be extended to any type of VSI and any modulation scheme, (ii) it can be applied to analyze the power losses of VSIs during any desired period, and (iii) it can be easily implemented in any kind of the simulation software (e.g. Matlab/Simulink).