California

• Pacific Gas & Electric (PG&E)
• San Diego Gas & Electric (SDG&E)
• Southern California Gas (SoCalGas)

Connecticut

• Connecticut Natural Gas (CNG)
• Eversource (Formerly CL&P)
• Eversource (Formerly Yankee Gas)
• Southern Connecticut Gas (SCG)
• United Illuminating (UI)

Delaware

• Delmarva Power

District of Columbia

• Potomac Edison Power Company (PEPCO)
• Washington Gas Light (WGL)

Florida

• Central Florida Gas (CFG)
• Florida City Gas (FCG)
• Florida Public Utilities (FPU)
• Peoples Gas / TECO Gas

Georgia 

• Atlanta Gas Light

Illinois

• Ameren Utilities
• Commonwealth Edison (ComEd)
• MidAmerican Energy
• NICOR
• North Shore Gas
• Peoples Gas

Indiana

• Citizens Gas
• NIPSCO
• Vectren Energy Delivery

Maine 

• Bangor Gas Company
• Central Maine Power (CMP)
• Emera Main (Bangor Hydro)
• Maine Natural Gas
• Unitil

Maryland 

• Baltimore Gas & Electric (BG&E)
• Chesapeak Utilities
• Columbia Gas of Maryland
• Delmarva Power
• Potomac Edison Power Company (PEPCO)
• Potomac Edison
• Southern Maryland Electric Co-Op (SMECO)
• Washington Gas Light (WGL)

Massachusetts

• Berkshire Gas
• Columbia Gas of Massachusetts
• Liberty Utilities (Formerly New England Natural Gas)
• National Grid Massachusetts
• Eversource (Formerly NSTAR)
• Eversource (Formerly WMECO)
• Unitil (Formerly Fitchburg Gas & Electric)

Michigan 

• Consumers Energy
• Mich-Con DTE
• Michigan Gas Utilities
• SEMCO Energy

New Hampshire 

• Eversource (Formerly PSNH)
• Liberty Utilities (Formerly Granite State)
• Unitil

New Jersey

• Atlantic City Electric
• Elizabethtown Gas
• Jersey Central Power & Light (JCPL)
• New Jersey Natural Gas (NJNG)
• Public Service Gas & Electric (PSE&G)
• Rockland Electric
• South Jersey Gas

New York

• Central Hudson Gas & Electric
• Consolidated Edison (ConEd)
• National Fuel Gas
• National Grid
• New York State Electric & Gas (NYSEG)
• Orange & Rockland (O&R)
• Rochester Gas & Electric (RG&E)

Ohio

• AEP Ohio
• Cleveland Electric Illuminating (CEI)
• Columbia Gas of Ohio
• Dayton Power & Light (DP&L)
• Dominion East Ohio
• Duke Energy Ohio
• Ohio Edison (OE)
• Toledo Edison (TE)
• Vectren Energy Delivery

Pennsylvania

• Columbia Gas of Pennsylvania
• Duquesne Power
• Metropolitan Edison
• National Fuel Gas
• Pennsylvania Electric Company (Penelec)
• Penn Power
• Peoples Gas
• Philadelphia Electric Co. (PECO)
• Philadelphia Gas Works (PGW)
• PPL Electric (PPL)
• UGI Central Penn
• UGI Penn Natural Gas
• UGI Utilities
• West Penn Power

Rhode Island

• National Grid

Texas

• Atmos Energy
• AEP Texas Central
• AEP Texas North
• Centerpoint Energy
• Oncor
• Sharyland
• Texas-New Mexico Power (TNMP)