The utilization time of maximum power losses (UTL) is a parameter used at determination of the active energy losses in power grids, influencing the accuracy of their calculation. This parameter can be estimated by the maximum load time (MLT), since its values can easily be obtained from the readings of widely employed electricity meters. The known methods allow for UTL determination by the total value of MLT, which leads to considerable errors and ambiguous results. The proposed method is based on the load duration curve (LDC) decomposition into two parts: a base and a delta ones. Theoretically, for the base part the UTL can be calculated without errors. The range of errors for the delta part can be considerably narrowed, which will raise the accuracy of the entire LDC calculation. The delta part, according to the method, is reduced to the maximum of 1, which simplifies the UTL calculation. The method is verified on many groups of electricity consumers. The shape of the reduced LDC-delta can be used for identification of the type of electricity consumer.