United States:
Alabama Electric Cooperative Corporation
American Electric Power
Arizona Public Service
Commonwealth Edison (Exelon)
Consolidated Edison
Duke Energy
Duquesne Light
Electric Power Research Institute (EPRI)
Eugene Water and Electric Board (EWEB)
Hoosier Energy
Long Island Power Authority (LIPA)
Los Angeles Department Water Power (LADWP)
Michigan Electric Transmission (formerly Transelect, now ITC)
National Grid USA
National Rural Electric Cooperative Association (NRECA)
Nevada Power
New York Power Authority
Potomac Electric Power Company (PEPCO - division of PHI)
Rochester Gas & Electric (RG&E)
SunCoke Energy
United Water
Western Area Power Administration (WAPA)
Wisconsin Energy

Canadian Petroleum Services (CPS) - Toronto, Ontario, Canada and Dubai, UAE (for Qatar Petroleum and Kuwait Petroleum)
CVG Electrificación del Caroní (EDELCA) - Puerto Ordaz, Venezuela
Grupo EMEL - Santiago, Chile
Energía de Pacifico, SA (EPSA) - Cali, Colombia
ESKOM - Johannesburg, South Africa
Instituto Costarricense de Electricidad (ICE) - San José, Costa Rica
Interconexión SA (ISA) - Medellín, Colombia (with RCMC)
Ontario Power Generation - Toronto, Ontario, Canada
Polish Power Grid - Warsaw, Poland
United Energy - Melbourne, Victoria, Australia
Yunnan Power Grid - Kunming, Yunnan, China (with Meridium)