The equipment of many distribution companies in Poland is old, therefore investment projects should be implemented to modernize it. One of the key parameters that should be taken into account is energy loss. In the distribution network the highest loss is attested in meters, LV, MV and HV lines and in MV/LV transformers. This paper deploys the methods of SPBP, IRR and NPV to present an analysis of effectiveness of investment projects. The analysis is based on real input data from two distribution companies in Poland.