The losses represent mainly the energy dissipated due to the Joule effect during transmission over the high and extra high voltage network. They depend mainly on consumption, the generation plan and cross-border exchanges.
The system loss rates are included between 2 and 3.5% of consumption, depending on the seasons and time of day. On average, the rate comes to 2.5%, which represents about 11.5 TWh (TeraWatt-hours) per year.

Each week, RTE draws up loss forecasts for the coming week. These forecasts are established on the basis of predicted consumption, generation and exchanges. They are made available to those concerned on the Web site on Thursday (12 a.m.). These forecasts are refined two days before so as to take into account the meteorological conditions. These forecasts are refined on day D-2 according to the latest meteorological forecasts. They are then used to establish the delivery programmes sent to suppliers with whom RTE has signed energy exchange contracts.

If you would like to know more about the predictions for power losses on the THT network in the medium and long term, consult the article presented at the time of days CIGRE of September 2004.