ATP-dependent proteases are crucial to maintain cellular protein homeostasis. Here we used single-molecule assays to characterize the mechanism by which the AAA+ protease ClpXP from E. coli transforms energy from ATP hydrolysis into mechanical work to drive protein translocation and unfolding. We establish that ATP hydrolysis and phosphate release occur in the burst phase during conformational changes of the motor, while ADP release and ATP binding happen in the dwell between bursts. We find that the residues of the highly-conserved translocating pore loops in the central ClpX pore determine the efficiency of substrate unfolding and translocation, and are crucial for the mechanochemical coupling and the power generated by ClpXP. Interestingly, we observe that the conformational resetting of the pore loops between consecutive power strokes appears to time both the dwell duration and the release of ADP. Together, our results indicate that: i) the mechanochemical coupling of the motor and its unfolding capability are mediated by the size of the residues in the translocating loops, ii) the unfolding capability of the motor does not depend on the burst size or the grip as previously proposed, but instead it depends on the power -work produced per unit time- generated by the motor, iii) provide insights into why evolution has selected a conserved sequence-motif for the translocating loops of prokaryotic and eukaryotic AAA+ proteases, and iv) indicate that ClpXP's mechanism deviates from other well studied molecular motors (such as the Phi29 DNA packaging motor).