Today＇s typical vertically integrated utility sells electricity and associated services as a bundled product. These ancillary services support and make possible the provision of the basic services of generating capacity, energy supply, and power delivery. These ancillary services include the following: management of generating units; reserve generating capacity to follow variations in customer loads, to provide capacity and energy when generating units or transmission lines suddenly fail, to maintain electric-system stability, and to provide local-area security; transmission-system monitoring and control; replacement of real power and energy losses; reactive-power management and voltage regulation; transmission reserves; repair and maintenance of the transmission network; metering, billing, and communications; and assurance of appropriate levels of power quality.