© 2020 Elsevier LtdIn this study, thermodynamic inefficiencies of the components and the whole system are quantified by exergy destruction. The performance of an air source heat pump water heater (ASHPWH) is examined experimentally under varying ambient conditions from the exergy destruction aspect. The exergy destruction is calculated for each moment through the entire heating period with regard to collected temperature and pressure data under various ambient conditions. The exergy destructions are examined continuously in a sequence from the beginning to the end of the water heating process. This approximation allows the designer and the manufacturer to see the progress of exergy destruction through the entire heating period to evaluate the performance of every component for avoiding irreversibilities and improving the ASHPWH. During these observations, three individual zones are observed in which the exergy destruction characteristics have changed. Furthermore, the impact of the ambient conditions on these zones is identified either. The thermodynamic properties and exergy destruction values are computed for all data collected by a MATLAB code. The results would be helpful to picture out the true evolution of the exergy destruction from component aspect either solely or combined effect of them during the water heating period.