This paper introduces a condition monitoring (CM) algorithm based on the circuit breaker (CB) arcing power and its related energy to estimate the electrical wear of arcing contacts. There is an electric arc occurring between the CB arcing contacts mainly during opening operations. Instantaneous voltage across the terminals of the CB and instantaneous current going through the CB are measured to calculate the arcing power and its related energy, which only exist under arcing events. Therefore, the power-based algorithm does not require the time synchronization to the power system frequency for measuring the CB arcing powers. The cumulative arcing energy of the CB is a good indication of the degradation level of arcing contacts and it is used to estimate the CB contact wear. Unlike the current-based CM method, the proposed power-based algorithm detects arc restrikes that produce more arcing energies and cause a greater contact wear. Thus, it allocates a higher amount of contact wear for interruptions with arc restrikes that makes it a more reliable and accurate technique. The outcomes of computer simulation and real-time test studies demonstrate that the power-based method can estimate the electrical wear of arcing contacts accurately, and thus, provides accurate inspection or maintenance times of CB's arcing contacts.