Previous utility participants include:

Alabama Power
Allete
American Electric Power (AEP)
American Municipal Power
Arizona Public Service (APS)
Atmos Energy Corporation
Austin Energy
Avista Corporation
Bangor Hydro Electric Company
Black Hills Corporation
Black Hills Utility
Holding, Inc
Bluewater Power Corporation
Bonneville Power Administration
Brownsville Public Utilities
CenterPoint Energy
Citizens Energy Group
City of Riverside-Public Util.
Cobb Energy
Colorado Springs Utilities
Con Edison
Consumers Energy
CPS Energy
Dayton Power & Light
Delta-Montrose Electric Association
Dominion
DTE Energy
Duke Energy
Energy Future Holdings
Entergy
Exelon Corporation
Florida Power & Light (FPL)
Great River Energy
Gulf Power
Idaho Power
Imperial Irrigation District
Integrys
JEA
Kansas City Power & Light (KCP&L)
LA Dept. of Water & Power
Laclede Gas Company
LCRA
Lee County Electric Cooperative (LCEC)
Liberty Power
Nashville Electric Service
National Fuel Gas
National Grid
Nebraska Public Power District
New York Power Authority
Nicor
NISource inc
Northeast Utilities
Northwest Natural Gas
NSTAR
OGE Energy Corporation
Omaha Public Power District
Pacific Gas and Electric Company (PG&E)
PEPCO Holdings, Inc.
Platte River Power Authority
PNM Resources
Portland General Electric
PPL Electric Utilities
Progress Energy
Salt River Project (SRP)
San Diego Gas & Electric
Santee Cooper
SCANA Corporation
SMUD
Southern California Edison
Southern Company
Southwest Gas Corporation
Southwest Power Pool
Toronto Hydro
Tucson Electric Power
U.S. Gas & Electric
UniSource Energy
Vectren Corporation
Wabash Valley Power
Xcel Energy