Line losses occur when electricity is moved from generation sites to consumption sites. Loss volumes depend on the power carried, the distance over which it is carried, weather conditions and the characteristics of the grid. Though most of these factors are external, RTE works to minimise losses by making decisions about grid development and operation that optimise the distance over which electricity travels as much as possible. Nearly 80% of losses are due to the Heating of the conductor when an electric current flows through it and Physical phenomenon occurring when the conductor is exposed to high voltage on high and very high voltage lines. Other effects contribute as well, notably when current passes into transformer substations. The environmental impact of losses corresponds to the power that must be generated to offset them.
In 2018, losses on the RTE transmission network reached 11 TWh, which represented 2.16% of total injections (generation and imports).