One of the main goals of creating Future Networks is to reduce the energy for their operation through the use of various energy-saving technologies. The most important components of existing and future networks are Passive Optical Networks (PON), which are widely used for building broadband access networks. The methodology for measuring the power consumption of passive optical network equipment with time division multiplexing TDM-PON is discussed in the article. It is based on the materials of ITU-T Recommendations Y.3021 and Y.3022. Estimations of possible energy savings in the GPON network based on OLT and ONU equipment of the Russian company Eltex are obtained with the use of the doze mode and cyclic sleep mode.