The continuous growth of the number and installed power of the electric energy consumers and the growth of the density of consume in large urbanistic areas, led to the necessity of a durable development of the electric energy distribution systems. At present time, the estimation of the power and energy losses in the distribution systems is done with difficulty, mainly, because of the lack of instruments installed in the nodes of the networks that allow the continuous record of the loads. In the paper, there are presented two methodologies: the decomposition of the load curves into Fourier series and the sampling of the load curves. On these bases there were realized packages of software that estimate the power and energy losses in electric distribution systems. The input data need a low number of measurements in the network and the results have a good precision.
