Network reconfiguration for energy loss reduction is one of the important issues in distribution network operations. Conventionally, many research studies focused on developing configuration optimization methods. However, there are no quan titative reports on the potential of energy loss reduction in long- term operations based on real network and power measurement data. Therefore, this paper reveals energy loss reduction effects of the energy-loss minimum operation. For this evaluation, this paper applies an integrated evaluation method including load estimation, configuration optimization, and operational evalua tion. Experiments were conducted using two Japanese substation- scale networks (1435-bus network and 1817-bus network) with annual power measurement data. Current utility operations were compared to the practical energy-loss minimum operations. Compared with the current operation, the optimal operation changing remote and manual switches seasonally reduced energy loss up to 112.06 MWh (6.4%) and 73.48 MWh (3.2%) for 1435- bus network and 1817-bus network.