What are the two center of powers during the middle ages?

Answer 1

You could make a case for two centers of power being Rome and Constantinople. Or the two centers could be Rome and Avignon. Possibly Popes and Monarchs could be the answer. You might even find someone advocating for Lübeck and Venice as power centers.

Answer 2

• Alabama --- AECO (Alabama Electric Company), Alabama Power, a part of the Southern Company, PowerSouth Energy Cooperative, Inc., Wiregrass Electric Cooperative, Tennessee Valley Authority
• Alaska --- Golden Valley Electric Association, Chugach Electric Association, Copper Valley Electric Association, Municipal Light & Power, Kodiak Electric Association, Alaska Villages Electric Cooperative
• Arizona --- Arizona Public Service, Salt River Project, Tucson Electric Power
• Arkansas --- Entergy, North Little Rock Electric
• California --- Alameda Municipal Power, Anaheim Public utilities, Azusa Light & Water, City of Palo Alto Utilities, California Public Utilities Commission, Bear Valley Electric, Burbank Water & Power, Colton Public Utilities Glendale Public Service Department, Gridley Municipal Utilities, Healdsburg Municipal Electric Department, City & County of San Francisco, Imperial Irrigation District, Los Angeles Department of Water and Power, Mountain Utilities, Pacific Gas & Electric, PacifiCorp, Pasadena Water & Power, Riverside Public Utilities, Sacramento Municipal Utility District, Silicon Valley Power, San Diego Gas & Electric, Sierra-Pacific Power, Southern California Edison, Southern California Public Power Authority, Surprise Valley power, Vernon Light & Power, Valley Electric association
• Colorado --- Xcel Energy, Colorado Springs Utilities, United Power Inc, Holy Cross Energy Company
• Connecticut --- Northeast Utilities (including Connecticut Light & Power), United Illuminating, Connectict Natural Gas, Yankee Gas, Wallingford Electric
• Delaware --- Calpine, Delmarva Power (a subsidiary of Pepco Holdings, Inc.), City of Milford Electric Department, Delaware Electric Cooperative, NRG Energy
• District of Columbia --- PEPCO
• Florida --- Florida Power & Light, TECO, Progress Energy Florida, Lake Worth Utilities, JEA, Lakeland Electric, Gulf Power, a part of the Southern Company, Kissimmee Utility Authority, Ocala Electric, Florida Public Utility Company Palm Beach, Florida Municipal Power Agency, LCEC, Gainesville Regional Utilities, City of Tallahassee utilities, Orlando Utilities Commission
• Georgia --- Georgia Power , a part of the Southern Company, Flint Energies, Tennessee Valley Authority
• Hawaii --- Hawaiian Electric Industries, Hawaiian Electric Company (HECO), Kauai Island Utility Cooperative (KIUC)
• Idaho --- IDACORP, Clearwater Power, PacifiCorp (Rocky Mountain Power)
• Illinois --- Ameren, Springfield City Water, Light & Power, ComEd, Batavia Municipal Electric ComEd Electric Company
• Indiana --- Duke Energy, Cinergy Corporation, Indianapolis Power & Light, Northern Indiana Public Service Company, American Electric Power
• Iowa --- MidAmerican Energy, Interstate Power and Light Company-a part of Alliant Energy
• Kansas --- Kansas City Power & Light, Westar Energy, Kansas City Board of Public Utilities
• Kentucky --- Kentucky Utilities, Louisville Gas & Electric, Cinergy Corporation, American Electric Power, Owensboro Municipal Utilities, Tennessee Valley Authority, Big Rivers Electric Corporation, Henderson Municipal Power and Light
• Louisiana --- SWEPCO (a subsidiary of American Electric Power), Entergy, CLECO
• Maine --- Central Maine Power, Bangor Hydro Electric
• Maryland --- Allegheny Power, Baltimore Gas & Electric, Choptank Electric Cooperative, PEPCO, Delmarva Power (subsidiary of Pepco Holdings), Southern Maryland Electric Cooperative
• Massachusetts --- Massachusetts Municipal Wholesale Electric Company (MMWEC), NSTAR, Northeast Utilities (including Western Massachusetts Electric, Berkshire Company/WMECO), National Grid (including Nantucket Electric and Massachusetts Electric), Peabody Municipal Light Plant
• Michigan --- Consumers Energy, DTE Energy (Detroit Edison), Excel Energy(Upper Peninsula), We Energies, American Electric Power, Wyandotte Municipal Services City of Wyandotte only, Holland Board of Public Works, Lansing Board of Water & Light, Upper Peninsula Power Company
• Mississippi --- Entergy, Southwest Mississippi Electric Power Association, Magnolia Electric, Mississippi Power company, a part of the Southern Company, Tennessee Valley Authority
• Minnesota --- Xcel Energy, Great River Energy (and its 28 member cooperatives), Minnkota Power Cooperative (and its 11 member cooperatives), Basin Electric Power Cooperative, East River Electric Power Co-op, Alliant Energy, ITC Midwest, L&O Power Co-op, Minnesota Power, Otter Tail Power Company, People's Co-op, Tri-County Electric, 125 municipally-owned electric utilities including Rochester Public Utilities, Hutchinson Utilities Commission, Marshall Municipal Utilities, municipal joint action (power supply) agencies including Missouri River Energy Services.
• Missouri --- Ameren, Kansas City Power & Light, Empire District Electric Company, New-Mac Electric, City Utilities of Springfield, Independence Power and Light
• Montana --- Northwestern Energy, MDU, Central Montana Electric Power Cooperative, Montana Electric Cooperatives' Association (and its 25 member cooperatives)
• Nebraska --- Omaha Public Power District, Nebraska Public Power District
• Nevada --- NV Energy (Nevada Power, Sierra Pacific Power)
• New Hampshire --- Northeast Utilities (including Public Service of NH), National Grid (including Granite State Electric), Unitil Corporation
• New Jersey --- Atlantic City Electric (A subsidiary of Pepco), Public Service Electric and Gas Company (PSE&G), Northeast Utilities, FirstEnergy, Jersey Central Power and Light Company (A subsidiary of GPU Energy, which is a subsidiary of GPU; all of which is now part of FirstEnergy), Vineland Municipal Electric Utility, Sussex Rural Electric Cooperative (New Jersey's sole Electric Cooperative)
• New Mexico --- Public Service Company of New Mexico, Farmington Electric Utility System
• New York --- CH Energy Group (formerly Central Hudson Gas & Electric), Consolidated Edison Company of New York (Con Edison), Citizens Choice Energy Jamestown BPU, Green Island Power Authority (Village of Green Island only), Long Island Power Authority (LIPA), National Grid (including Niagara Mohawk), New York Power Authority (NYPA), New York State Electric & Gas (NYSEG), Rochester Gas & Electric
• North Carolina --- Progress Energy Carolinas, Duke Energy, ElectriCities, North Carolina Electric Membership Corp.
• North Dakota --- Xcel Energy, Otter Tail Power Company, MDU, Central Power Electric Cooperative, Minnkota Power Cooperative, Basin Electric Power Cooperative, Upper Missouri G&T Cooperative
• Ohio --- Cinergy Corporation, FirstEnergy (Cleveland Electric Illuminating Company, Ohio Edison, Toledo Edison), American Electric Power, Dayton Power & Light, South Central Power Company, Consolidated Electric Cooperative
• Oklahoma --- Oklahoma Gas & Electric, Public Service Company of Oklahoma (part of American Electric Power)
• Oregon --- Columbia River Public Utility District, Eugene Water & Electric Board, PacifiCorp (Pacific Power), Portland General Electric, West Oregon Electric Cooperative, Canby Electric, Salem Electric, Emerald PUD, Tillamook PUD, Ashland Electric, Wasco Electric
• Pennsylvania --- Rural Valley Electric Co., FirstEnergy (Penn Power, Met-Ed, Penelec), PECO, Allegheny Power, PPL, Duquesne Light, Citizens Electric of Lewisburg, Pike County Light & Power Company, UGI Utilities, Inc. and Wellsboro Electric Company
• Puerto Rico --- Autoridad de Energía Electrica, EcoEléctrica
• Rhode Island --- National Grid (including Narragansett Electric)
• South Carolina --- Santee Cooper, Duke Energy, Central Electric Power Cooperative, Inc., Progress Energy Carolinas, South Carolina Electric & Gas Company, Berkeley Electric Cooperative
• South Dakota --- Xcel Energy, Otter Tail Power Company, Montana-Dakota Utilities, Northwestern Energy, Black Hills Power, East River Electric Cooperative, Rushmore Electric Cooperative
• Tennessee --- Citizens Utilities Board, Electric Power Board, Knoxville Utilities Board, Kingsport Power (Appalachian Power), Lenoir City Utilities Board, Memphis Light, Gas and Water, Nashville Electric Service, Tennessee Valley Authority, Jackson, Tennessee Jackson Energy Authority
• Texas --- American Electric Power, Austin Energy, CPS Energy, dPi Energy, Electric Database Publishing, First Texas Energy Corporation, Garland Power and Light, Luminant, Reliant Energy, CenterPoint Energy, Texas Electric Service Company, Lower Colorado River Authority, Magic Valley, Oncor Electric (Formerly TXU), Coserv Electric, Denton Municipal Electric, Entergy
• Utah --- Intermountain Power Agency, PacifiCorp (Rocky Mountain Power)
• Vermont --- Central Vermont Public Service, Green Mountain Power
• Virginia --- Dominion Virginia Power, Rappahannock Electric Cooperative, Allegheny Power, Appalachian Power, Delmarva Power (subsidiary of Pepco Holdings), NOVEC, Danville Utilities (municipally owned)
• Washington --- PacifiCorp (Pacific Power), Puget Sound Energy, Seattle City Light, Snohomish County Public Utility District (PUD), Mason County Public Utility District 3, Klickitat Public Utility District, Avista Utilities, Grant County Public Utility District, Chelan County Public Utility District, Douglas County Public Utility District, Tacoma Power, Benton PUD
• West Virginia --- Allegheny Power, Appalachian Power, Wheeling Electric Power (AEP Ohio)
• Wisconsin --- Dairyland Power Co-op, We Energies, Wisconsin Public Service Corporation, Xcel Energy, Wisconsin Power and Light Company--a part of Alliant Energy, Madison Gas and Electric
• Wyoming --- PacifiCorp (Rocky Mountain Power), High Plains Power, Lower Valley Energy