High-speed data transfer over power grids is ensured by PLC technology supported by different worldwide standards. Realization of this technology is advantageous especially in buildings where there is no data network or other transfer medium. PLC technology can be used as an alternative way to Wi-Fi, for example, due to wall width when Wi-Fi is not usable. This technology has been often given in relation with possible usage in smart homes. Installation of modems is easy and fast. After connection of PLC modem in power supply, data are available in power grid at home or in a building.