| Company | Sector | Type |
| A&C Management Group LLC* | | Emergency Load Program Member |
| AC Energy, LLC | Other Supplier | Voting Member |
| AC Power Financial Corp. | Other Supplier | Voting Member |
| Acciona Energy North America Corporation (AENAC) | Generation Owner | Voting Member |
| AEP Appalachian Transmission Company, Inc. | Transmission Owner | Affiliate |
| AEP Energy Partners, Inc. | Other Supplier | Affiliate |
| AEP Indiana Michigan Transmission Company, Inc. | Transmission Owner | Affiliate |
| AEP Kentucky Transmission Company, Inc. | Transmission Owner | Affiliate |
| AEP Ohio Transmission Company, Inc. | Transmission Owner | Affiliate |
| AEP Retail Energy Partners LLC | Other Supplier | Affiliate |
| AEP West Virginia Transmission Company, Inc. | Transmission Owner | Affiliate |
| AES Armenia Mountain Wind, LLC | Generation Owner | Affiliate |
| AES Beaver Valley, LLC | Generation Owner | Voting Member |
| AES Energy Storage, LLC | Generation Owner | Affiliate |
| AES Ironwood, LLC | Generation Owner | Affiliate |
| AES Laurel Mountain, LLC | Generation Owner | Affiliate |
| AES Red Oak, LLC | Generation Owner | Affiliate |
| Air Liquide Industrials U.S., L.P. | End User Customer | Voting Member |
| Air Products & Chemicals, Inc. | End User Customer | Voting Member |
| AK Steel Corporation | End User Customer | Voting Member |
| Akula Energy, LLC | Other Supplier | Affiliate |
| Alcoa Power Marketing LLC | Other Supplier | Voting Member |
| Algonquin Energy Services Inc. | Other Supplier | Voting Member |
| Allegheny Electric Cooperative, Inc. | Transmission Owner | Voting Member |
| Allegheny Energy Supply Company, L.L.C. | Transmission Owner | Affiliate |
| ALLETE, Inc. d/b/a Minnesota Power | Other Supplier | Voting Member |
| Alliant Energy Corporate Services, Inc. | Other Supplier | Voting Member |
| Alpha Gas and Electric, LLC | Other Supplier | Voting Member |
| Ambit Northeast, LLC | Other Supplier | Voting Member |
| Ameren Energy Marketing Company | Other Supplier | Voting Member |
| American Municipal Power, Inc. | Generation Owner | Voting Member |
| American Power Partners LLC | Other Supplier | Affiliate |
| American PowerNet Management, L.P. | End User Customer | Voting Member |
| American Transmission Company, LLC | | Associate Membership |
| American Transmission Systems, Inc. | Transmission Owner | Affiliate |
| Amerigreen Energy, Inc. | Other Supplier | Voting Member |
| Analytical Applications* | | Emergency Load Program Member |
| Anbaric Northeast Transmission Development Company, LLC | Other Supplier | Voting Member |
| AP Gas & Electric (IL), LLC | Electric Distributor | Affiliate |
| AP Gas & Electric (MD), LLC | Other Supplier | Affiliate |
| AP Gas & Electric (NJ), LLC | Electric Distributor | Affiliate |
| AP Gas and Electric (PA), LLC | Other Supplier | Voting Member |
| APN Starfirst, LP | End User Customer | Affiliate |
| Appalachian Power Company | Transmission Owner | Voting Member |
| Apple Group LLC | Other Supplier | Voting Member |
| APX Power Markets Inc. | | Associate Membership |
| Aquenergy Systems Inc. | Generation Owner | Voting Member |
| ArcelorMittal USA LLC | End User Customer | Voting Member |
| ArcLight Energy Marketing, L.L.C. | Other Supplier | Voting Member |
| Aspen Merchant Energy, LP | Other Supplier | Affiliate |
| Associated Electric Cooperative, Inc. | Other Supplier | Voting Member |
| Astral Energy LLC | Other Supplier | Voting Member |
| Atlantic City Electric Company | Electric Distributor | Affiliate |
| Atlantic Grid Operations A, LLC | Other Supplier | Voting Member |
| Automated Algorithms, LLC | Other Supplier | Voting Member |