Unlike the mobile, onboard Sibac ES energy storage system, Sitras SES is permanently integrated into the traction power supply system. Consequently, excess energy that has been recovered within a network, e.g. from braking, is temporarily buffered and released again when required.

Sitras SES has been successfully installed in numerous mass transit systems. Two operating modes are available. On the one hand, Sitras SES can be used as a temporary buffer store. The energy recovered when the vehicles are in braking mode is stored and made available for subsequent use. Depending on the system installed, up to 500,000 kWh of the primary energy requirement can be saved, corresponding to almost one-third of the annual consumption. This reduces annual CO₂ emissions by about 300 tons.

On the other hand, Sitras SES acts as a voltage stabilizer, especially during traffic peaks, to prevent the line voltage from dropping below a critical level. As a result, Sitras SES greatly increases voltage stability in the power system and thus prevents downtimes due to power outages. In addition, fewer voltage drops means fewer losses in the system..