The development of a distributed generation will influence the structure of the power transmission and distribution network. Distributed sources have lower power and therefore the lines of lower voltage are used. Therefore, the electric field intensity near such lines is lower. On the other hand magnetic field intensity may prove essential. The main aim of the paper is to present a method estimating the “ballast” of the natural environment at 50 Hz electric and magnetic fields in the power system, with distributed and centralized generation in real operating conditions.