Energy losses in electrical networks are usually estimated by balancing fed and delivered energy of an analyzed network area. Generally, it is not possible to derive information for loss reduction opportunities from these data. Furthermore, there is no possibility to distinguish between technical and non-technical losses. The proposed method calculates network losses in low voltage networks and takes the effect of short-time load peaks as well as unbalanced loads into consideration by using standard load profiles in connection with an obtained Loss Correction Function. The loss is calculated for each relevant line, so it provides the option to point out high-loss areas or equipment owning a high potential for loss reduction, to allow optimized investments in development and maintenance of the investigated electrical system.