Ancillary Services

Services necessary to support the transmission of electric power.

Last Updated:  June 20, 2025

Definition by FERC

Source:

Those services necessary to support the transmission of electric power from seller to purchaser, given the obligations of control areas and transmitting utilities within those control areas, to maintain reliable operations of the interconnected transmission system. Ancillary services supplied with generation include load following, reactive power-voltage regulation, system protective services, loss compensation service, system control, load dispatch services, and energy imbalance services.

More details can be found in the Reference Appendix I: Regional Practices for Ancillary Services.