In H2-supported microgrids, the electrochemical performance deterioration of reversible solid oxide cell (rSOC) is primarily caused by the coarsening of Ni particles. Specifically, there are still various unresolved questions from microdegradation mechanisms to macroperformance optimization of rSOC systems that require further investigation and solutions. In this study, a novel multiscale-multiphysics field model consisting of a modified Ni coarsening model incorporated into the rSOC system model is used to analyze the effects of operating modes and conditions on degradation behavior. The issue of coordination between degradation and efficiency is settled for the first time by introducing minimization of the total operating cost of an rSOC system. The results indicate that the degradation rate (rdeg) is higher in the fuel cell mode, and this is related to the partial pressure ratio pH2/pH2O within H2-electrode pores. Furthermore, rdeg is found to be most affected by the PEN temperature, followed by the fuel utilization and fuel molar fraction. The minimum total cost is approximately 0.49 $/kWh taken at a low system intake (including H2O, H2, and air) with higher temperatures. The optimization weight shifts gradually toward efficiency owing to the higher gas supply cost. These findings provide a valuable reference for the selection of the optimal operating state for the rSOC system considering degradation.