In this paper, we investigate the energy efficiency performance of Multiple-Input-Multiple-Output (MIMO) relayassisted Power Line Communication (PLC) networks. We consider a half-duplex Decode and Forward (DF) relay system and compare its performance for both uniform time allocation and optimized time allocation strategies. Based on realistic MIMO PLC channels, obtained from the European Telecommunications Standards Institute (ETSI) Specialist Task Force (STF) 410 field measurement campaign that was performed in six European countries, we show that depending on the idle power consumption of MIMO PLC modems in the relay network, possible energy saving gain can be obtained by using DF MIMO PLC relays.