Experimental data characterizing indoor electric and magnetic fields radiated by power line communication (PLC) systems and used for the calculation of a local transfer function (coupling factor) are presented. It is shown that the indirect determination of electric field using magnetic field measurements and assuming a plane wave approximation may result in an underestimation of the electric field. Additionally, it is shown that the radiated field magnitudes vary significantly as a function of the position of the observation point and of the network load. A first evaluation of the indoor electromagnetic field radiated by PLC systems using NEC2 is presented and compared with experimental data.