Electricity transmission losses refer to the amount of electrical energy that is dissipated or "lost" as it travels through transmission lines from the power source to the end-user. These losses primarily occur as heat and are an unavoidable consequence of the physical properties of conductors. The goal of all power grid operators is to minimize these losses to ensure the highest possible efficiency.

A key indicator of power grid efficiency, transmission and distribution losses typically range from 2% to 8% of the total electricity generated, depending on the network's design, length, and technology.