For a few years, MIMO technique has been considered as the key to increase the data rate in the next generation of power line communications. The HomePlug AV2 and ITU-T G.9963 technologies exploit the MIMO scheme to increase both data rate and coverage. In this paper, an improvement of MIMO-PLC modeling is derived and the analytic formula of the interference is developed. Based on the interference analysis, the signal to interference plus noise ratio (SINR) is calculated and compared to the signal to noise ratio (SNR). Finally, the degradation of system performance in terms of capacity due to the interference is shown.