| 1 | Centrica PLC | Unitedkingdom | Windsor | Millstream | Windsor and Maidenhead | SL4 5GD | centrica.***** | 1995 | $25,243,351,666 | 21,704 | N/A | N/A | N/A |
| 2 | Edf Energy Customers LIMITED | Unitedkingdom | London | Nova North | London | SW1E 5BY | N/A | 1988 | $17,306,394,664 | 3,708 | N/A | N/A | N/A |
| 3 | E.ON Next Energy LIMITED | Unitedkingdom | Aldermans Green | E on UK Plc | Coventry, West Midlands | CV4 8LG | eonenergy.***** | 1990 | $15,362,311,375 | 3,321 | N/A | N/A | N/A |
| 4 | Edf Energy LIMITED | Unitedkingdom | London | Nova North | London | SW1E 5BY | N/A | 1989 | $13,453,909,066 | 819 | N/A | N/A | N/A |
| 5 | E.ON UK Energy Markets LIMITED | Unitedkingdom | Aldermans Green | Westwood Way | Coventry, West Midlands | CV4 8LG | gienergy.***** | 2015 | $10,314,249,625 | 93 | N/A | N/A | N/A |
| 6 | Ovo Energy LTD | Unitedkingdom | Bristol | Temple Quay | City of Bristol | BS1 6DG | ovoenergy.***** | 2009 | $10,178,388,210 | 4,169 | N/A | N/A | N/A |
| 7 | Octopus Energy LIMITED | Unitedkingdom | Marylebone | 1 Upper James Street | London | W1F 9DE | octopus.***** | 2014 | $10,069,767,254 | 1,739 | N/A | N/A | N/A |
| 8 | Scottishpower Energy Retail LIMITED | Unitedkingdom | Glasgow | Scottishpower House | Glasgow City | G2 5AD | scottishpower.***** | 1998 | $9,486,118,211 | 925 | N/A | N/A | N/A |
| 9 | Npower Commercial Gas LIMITED | Unitedkingdom | Aldermans Green | Westwood Way | Coventry, West Midlands | CV4 8LG | N/A | 1990 | $8,275,894,641 | 1,006 | N/A | N/A | N/A |
| 10 | Drax Group PLC | Unitedkingdom | Moorgate | 10 Noble Street | London | EC2V 7JX | draxteachingzone.***** | 2005 | $7,812,090,325 | 3,457 | N/A | N/A | N/A |
| 11 | Shell Energy Europe LIMITED | Unitedkingdom | Herne Hill | Shell Centre | London | SE1 7NA | shell.***** | 2001 | $7,555,975,966 | 230 | N/A | N/A | N/A |
| 12 | Cnooc U.K. Marketing LTD | Unitedkingdom | Marylebone | Level 6 | London | W1H 6AZ | N/A | 2019 | $7,379,575,000 | 230 | N/A | N/A | N/A |
| 13 | Scottishpower Energy Management LIMITED | Unitedkingdom | Cathcart | Spean Street Cathcart Business Park | Glasgow City | G44 4BE | N/A | 2001 | $7,075,762,208 | 58 | N/A | N/A | N/A |
| 14 | British Gas LIMITED | Unitedkingdom | Windsor | Millstream | Windsor and Maidenhead | SL4 5GD | britishgas.***** | 2013 | $6,960,841,862 | 286 | N/A | N/A | N/A |
| 15 | Sefe Marketing & Trading LIMITED | Unitedkingdom | Saint Johns Wood | 20 Triton Street | London | NW1 3BF | gazprom-mt.***** | 1999 | $6,690,777,076 | 749 | N/A | N/A | N/A |
| 16 | Drax Power LIMITED | Unitedkingdom | Selby | Drax Power Station | North Yorkshire | YO8 8PH | drax.***** | 2003 | $6,290,745,157 | 708 | N/A | N/A | N/A |
| 17 | Totalenergies Gas & Power LIMITED | Unitedkingdom | Canary Wharf | 10 Upper Bank Street | London | E14 5BF | totalgp.***** | 1987 | $6,062,757,620 | 795 | N/A | N/A | N/A |
| 18 | Statkraft Markets GMBH | Unitedkingdom | Moorgate | : 19th Floor | London | EC2N 4BQ | statkraft.***** | 2018 | $5,336,099,920 | 30 | N/A | N/A | N/A |
| 19 | Edf Energy Nuclear Generation LIMITED | Unitedkingdom | Gloucester | Building 1420 Javelin House | Gloucestershire | GL3 4AE | N/A | 1995 | $5,120,167,598 | 5,366 | N/A | N/A | N/A |
| 20 | Octopus Energy Operations 2 LIMITED | Unitedkingdom | Coventry | Octopus Energy Ltd | Coventry, West Midlands | CV1 2GN | N/A | 2004 | $5,111,725,170 | 1,246 | N/A | N/A | N/A |
| 21 | B.B. Energy Trading LIMITED | Unitedkingdom | Ladbroke Grove | Bb House | London | W8 5BN | bbenergy.***** | 2002 | $5,029,677,000 | 73 | N/A | N/A | N/A |
| 22 | National Energy System Operator LIMITED | Unitedkingdom | Sindlesham | St Catherine'S Lodge | Wokingham | RG41 5BN | N/A | 2024 | $4,834,043,799 | 1,246 | N/A | N/A | N/A |
| 23 | Drax Energy Solutions LIMITED | Unitedkingdom | Selby | Drax Power Station | North Yorkshire | YO8 8PH | havenpower.***** | 2006 | $4,260,239,316 | 405 | N/A | N/A | N/A |
| 24 | Sse Energy Supply LIMITED | Unitedkingdom | Reading | No.1 Forbury Place | Reading | RG1 3JH | sseplc.***** | 1999 | $4,053,032,890 | 951 | N/A | N/A | N/A |
| 25 | Sse Hornsea LIMITED | Unitedkingdom | Reading | 43 Forbury Road | Reading | RG1 3JH | N/A | 2002 | $3,756,060,916 | 92 | N/A | N/A | N/A |
| 26 | National Grid Electricity Transmission PLC | Unitedkingdom | Marylebone | 1 - 3 Strand | London | WC2N 5EH | nationalgrid.***** | 1989 | $3,312,995,715 | 6,102 | N/A | N/A | N/A |
| 27 | E.ON UK PLC | Unitedkingdom | Aldermans Green | Westwood House | Coventry, West Midlands | CV4 8HS | eonenergy.***** | 1989 | $3,231,321,418 | 905 | N/A | N/A | N/A |
| 28 | National Grid Electricity Distribution PLC | Unitedkingdom | Saint Philips | Avonbank | City of Bristol | BS2 0TB | nationalgrid.***** | 2014 | $3,133,620,842 | 7,102 | N/A | N/A | N/A |
| 29 | Sefe Energy LIMITED | Unitedkingdom | Manchester | No 8, First Street | Manchester, Greater Manchester | M15 4RP | gazprom-energy.***** | 2000 | $2,997,477,992 | 277 | N/A | N/A | N/A |
| 30 | Ep UK Investments LTD | Unitedkingdom | London | Byron House | London | SW1A 1EE | putnam.***** | 2014 | $2,805,745,128 | 211 | N/A | N/A | N/A |
| 31 | Cadent Gas LIMITED | Unitedkingdom | Withybrook | Ansty Park Pilot Way | Warwickshire | CV7 9JU | cadentgas.***** | 2016 | $2,747,547,420 | 6,361 | N/A | N/A | N/A |
| 32 | Vpi Power LIMITED | Unitedkingdom | Edinburgh | Building 1 | City of Edinburgh | EH3 8RY | N/A | 2001 | $2,711,120,769 | 146 | N/A | N/A | N/A |
| 33 | Vpi Holding LIMITED | Unitedkingdom | London | 10th Floor | London | SW1E 5LB | vitol.***** | 2013 | $2,384,509,842 | 299 | N/A | N/A | N/A |
| 34 | Vpi Immingham Llp | Unitedkingdom | London | 160 Victoria Street | London | SW1E 5LB | vpi-i.***** | 2001 | $2,207,561,029 | 116 | N/A | N/A | N/A |
| 35 | Centrica Energy Marketing LIMITED | Unitedkingdom | Windsor | Millstream | Windsor and Maidenhead | SL4 5GD | centrica.***** | 2013 | $2,207,541,435 | 5 | N/A | N/A | N/A |
| 36 | Corona Energy Retail 4 LIMITED | Unitedkingdom | Watford | Building 2 | Hertfordshire | WD18 8YA | coronaenergy.***** | 1993 | $2,098,063,010 | 3 | N/A | N/A | N/A |
| 37 | Rwe Generation UK PLC | Unitedkingdom | Grange Park | Windmill Hill Business Park Whitehill Way | Swindon | SN5 6PB | rwe.***** | 1958 | $2,011,811,334 | 811 | N/A | N/A | N/A |
| 38 | UK Power Networks (operations) LIMITED | Unitedkingdom | Rotherhithe | Newington House | London | SE1 6NP | ukpowernetworks.***** | 2000 | $1,972,364,612 | 5,577 | N/A | N/A | N/A |
| 39 | Bulb Energy LTD | Unitedkingdom | Marylebone | United Kingdom House | London | W1D 1NN | N/A | 2013 | $1,965,679,560 | 2 | N/A | N/A | N/A |
| 40 | National Gas Transmission PLC | Unitedkingdom | Warwick | National Grid House | Warwickshire | CV34 6DA | nationalgrid.***** | 1986 | $1,961,991,735 | 2,244 | N/A | N/A | N/A |
| 41 | E D F Trading LIMITED | Unitedkingdom | London | 3rd Floor, Cardinal Place | London | SW1E 5JL | azurite.***** | 1999 | $1,540,797,616 | 593 | N/A | N/A | N/A |
| 42 | Txu UK LIMITED | Unitedkingdom | Ipswich | Wherstead Pk | Suffolk | IP9 2BJ | N/A | 1994 | $1,495,242,810 | 1,063 | N/A | N/A | N/A |
| 43 | Southern Electric Power Distribution PLC | Unitedkingdom | Reading | No.1 Forbury Place | Reading | RG1 3JH | sse.***** | 2000 | $1,438,793,939 | 3,004 | N/A | N/A | N/A |
| 44 | Keadby Generation LIMITED | Unitedkingdom | Scunthorpe | Scottish & Southern Energy Plc | North Lincolnshire | DN17 3EF | sse.***** | 1992 | $1,413,408,921 | 47 | N/A | N/A | N/A |
| 45 | Power Ni Energy LIMITED | Unitedkingdom | Antrim | Po Box 103 | Antrim and Newtownabbey | BT41 9BB | N/A | 1993 | $1,358,075,681 | 552 | N/A | N/A | N/A |
| 46 | Electricity Plus Supply LIMITED | Unitedkingdom | Mill Hill | 333 Edgware Road | London | NW9 6TD | N/A | 2004 | $1,356,531,173 | 3 | N/A | N/A | N/A |
| 47 | E.ON Energy Solutions LIMITED | Unitedkingdom | Aldermans Green | Westwood Way | Coventry, West Midlands | CV4 8LG | gienergy.***** | 1992 | $1,338,671,190 | 3,806 | N/A | N/A | N/A |
| 48 | Petredec (europe) LIMITED | Unitedkingdom | City of London | Level 43, the Leadenhall Building | London | EC3V 4AB | petredec.***** | 1980 | $1,268,528,000 | 9 | N/A | N/A | N/A |
| 49 | Brook Green Trading LIMITED | Unitedkingdom | Shepherd'S Bush | 245 Hammersmith Road | London | W6 8PW | N/A | 2015 | $1,254,716,465 | 2 | N/A | N/A | N/A |
| 50 | Brook Green Supply LIMITED | Unitedkingdom | Shepherd'S Bush | 245 Hammersmith Road | London | W6 8PW | brookgreensupply.***** | 2015 | $1,253,399,535 | 125 | N/A | N/A | N/A |
| 51 | Eastern Power Networks PLC | Unitedkingdom | Rotherhithe | Newington House | London | SE1 6NP | ukpowernetworksservices.***** | 1989 | $1,227,920,940 | 541 | N/A | N/A | N/A |
| 52 | Orsted Wind Power A/S | Unitedkingdom | London | Dong Energy | London | SW1P 1WG | orsted.***** | 2016 | $1,169,509,636 | 1,944 | N/A | N/A | N/A |
| 53 | Atlantica Sustainable Infrastructure LIMITED | Unitedkingdom | Chiswick | Building 7, Floor 2, Chiswick Business Park | London | W4 5YG | atlantishealthcare.***** | 2013 | $1,142,987,000 | 1,378 | N/A | N/A | N/A |
| 54 | Scottishpower Renewables (UK) LIMITED | Unitedkingdom | Glasgow | Scottishpower House | Glasgow City | G2 5AD | scottishpowerrenewables.***** | 1994 | $1,117,968,756 | 915 | N/A | N/A | N/A |
| 55 | So Energy Trading LIMITED | Unitedkingdom | Chiswick | Studio 2 Power Road Studios | London | W4 5PY | so.***** | 2014 | $1,089,570,195 | 442 | N/A | N/A | N/A |
| 56 | Scottish Hydro Electric Transmission PLC | Unitedkingdom | Buchanty | Inveralmond House | Perth and Kinross | PH1 3AQ | hydro.***** | 2000 | $1,020,842,895 | 2,084 | N/A | N/A | N/A |
| 57 | National Grid Electricity Distribution (west Midlands) PLC | Unitedkingdom | Saint Philips | Avonbank | City of Bristol | BS2 0TB | nationalgrid.***** | 1998 | $1,011,861,502 | 2,118 | N/A | N/A | N/A |
| 58 | Southern Gas Networks PLC | Unitedkingdom | Horley | St. Lawrence House | Surrey | RH6 9HJ | sgn.***** | 2004 | $1,010,723,015 | 304 | N/A | N/A | N/A |
| 59 | Shell Energy UK LIMITED | Unitedkingdom | Herne Hill | Shell Centre | London | SE1 7NA | shell.***** | 2013 | $1,003,210,575 | 139 | N/A | N/A | N/A |
| 60 | Sse Generation LIMITED | Unitedkingdom | Reading | No.1 Forbury Place | Reading | RG1 3JH | lightsoninsouthampton.***** | 1991 | $982,672,647 | 683 | N/A | N/A | N/A |
| 61 | Orlen Lng Trading LIMITED | Unitedkingdom | London | 3rd Floor | London | SW1P 1SB | N/A | 2022 | $980,670,495 | 21 | N/A | N/A | N/A |
| 62 | Engie Gas LIMITED | Unitedkingdom | New Wortley | No 1 Leeds, 26 Whitehall Road | Leeds, West Yorkshire | LS12 1BE | engie.***** | 1999 | $979,372,590 | 2 | N/A | N/A | N/A |
| 63 | National Grid Electricity Distribution (east Midlands) PLC | Unitedkingdom | Kegworth | Herald Way Pegasus Business Park | Leicestershire | DE74 2TU | nationalgrid.***** | 1989 | $972,393,970 | 2,058 | N/A | N/A | N/A |
| 64 | Sse Thermal Energy Operations LIMITED | Unitedkingdom | Reading | 43 Forbury Road | Reading | RG1 3JH | N/A | 2020 | $950,183,406 | 294 | N/A | N/A | N/A |
| 65 | Gas Plus Supply LIMITED | Unitedkingdom | Mill Hill | 333 Edgware Road | London | NW9 6TD | N/A | 2004 | $898,846,597 | 3 | N/A | N/A | N/A |
| 66 | Edf Energy Nuclear Generation Group LIMITED | Unitedkingdom | Glasgow | B D O Llp | Glasgow City | G2 8JX | N/A | 1989 | $858,622,793 | 61 | N/A | N/A | N/A |
| 67 | Sse Thermal Generation (scotland) LIMITED | Unitedkingdom | Buchanty | Inveralmond House | Perth and Kinross | PH1 3AQ | sse.***** | 2020 | $846,370,126 | 74 | N/A | N/A | N/A |
| 68 | South Eastern Power Networks PLC | Unitedkingdom | Rotherhithe | Newington House | London | SE1 6NP | ukpowernetworksservices.***** | 1995 | $846,274,965 | 13 | N/A | N/A | N/A |
| 69 | London Power Networks PLC | Unitedkingdom | Rotherhithe | Newington House | London | SE1 6NP | ukpowernetworks.***** | 2000 | $838,811,554 | 62 | N/A | N/A | N/A |
| 70 | Northern Powergrid (yorkshire) PLC | Unitedkingdom | Newcastle Upon Tyne | Lloyds Court | Newcastle Upon Tyne, Tyne and Wear | NE1 6AF | northernpowergrid.***** | 2000 | $832,972,292 | 1,229 | N/A | N/A | N/A |
| 71 | Ovo (s) Energy Services LIMITED | Unitedkingdom | Bristol | Temple Quay | City of Bristol | BS1 6DG | bristol-energy.***** | 2017 | $832,850,997 | 7,419 | N/A | N/A | N/A |
| 72 | Cfp Energy LIMITED | Unitedkingdom | Saint Helier | 5th Floor | Saint Helier | JE1 2TR | N/A | 2009 | $827,459,291 | 346 | N/A | N/A | N/A |
| 73 | Yu Energy Retail LIMITED | Unitedkingdom | Thorneywood | Cpk House | Nottingham | NG8 6PY | yuenergy.***** | 2012 | $814,938,247 | 338 | N/A | N/A | N/A |
| 74 | Sp Distribution PLC | Unitedkingdom | Glasgow | 20 York Street | Glasgow City | G2 8GT | N/A | 1998 | $782,540,099 | 838 | N/A | N/A | N/A |
| 75 | Electricity North West LIMITED | Unitedkingdom | Salford | Frederick Road | Manchester, Greater Manchester | M6 6QH | enwl.***** | 1989 | $759,055,289 | 2,103 | N/A | N/A | N/A |
| 76 | Orsted Power (UK) LIMITED | Unitedkingdom | London | 5 Howick Place | London | SW1P 1WG | orsted.***** | 2003 | $747,540,725 | 1,124 | N/A | N/A | N/A |
| 77 | Sp Manweb PLC | Unitedkingdom | Prenton | 3 Prenton Way | Wirral, Merseyside | CH43 3ET | spenergynetworks.***** | 1989 | $745,777,321 | 885 | N/A | N/A | N/A |
| 78 | Wales & West Utilities LIMITED | Unitedkingdom | Lower Machen | Wales & West House | Newport | NP10 8FZ | wwutilities.***** | 2004 | $698,398,219 | 1,932 | N/A | N/A | N/A |
| 79 | Calor Gas LIMITED | Unitedkingdom | Warwick | Athena House | Warwickshire | CV34 6RL | calor.***** | 1935 | $688,351,326 | 1,825 | N/A | N/A | N/A |
| 80 | Northern Powergrid (northeast) PLC | Unitedkingdom | Newcastle Upon Tyne | Lloyds Ct, 78 Grey St | Newcastle Upon Tyne, Tyne and Wear | NE1 6AF | northernpowergrid.***** | 1994 | $679,940,256 | 1,451 | N/A | N/A | N/A |
| 81 | Spalding Energy Company, LTD. | Unitedkingdom | Spalding | West Marsh Road | Lincolnshire | PE11 2BB | spaldingenergy.***** | 1996 | $678,855,866 | 410 | N/A | N/A | N/A |
| 82 | National Grid Electricity Distribution (south West) PLC | Unitedkingdom | Saint Philips | Avonbank | City of Bristol | BS2 0TB | nationalgrid.***** | 1989 | $678,664,453 | 1,720 | N/A | N/A | N/A |
| 83 | Ep Langage LIMITED | Unitedkingdom | London | Byron House | London | SW1A 1EE | N/A | 1997 | $666,040,021 | 40 | N/A | N/A | N/A |
| 84 | Sse Energy Markets LIMITED | Unitedkingdom | Reading | No.1 Forbury Place | Reading | RG1 3JH | N/A | 2015 | $664,887,253 | 276 | N/A | N/A | N/A |
| 85 | M Group Water (network Infrastructure) LIMITED | Unitedkingdom | Stevenage | Abel Smith House | Hertfordshire | SG1 2ST | morrisonus.***** | 1964 | $660,828,636 | 2,111 | N/A | N/A | N/A |
| 86 | Engie UK LIMITED | Unitedkingdom | City of London | Floor 4 the Broadgate Tower | London | EC2A 2EW | engie.***** | 1989 | $660,086,394 | 179 | N/A | N/A | N/A |
| 87 | Ep Lynemouth Power LIMITED | Unitedkingdom | Ashington | Woodhorn Village | Northumberland | NE63 9NW | lynemouthpower.***** | 2011 | $659,183,382 | 158 | N/A | N/A | N/A |
| 88 | Sp Transmission PLC | Unitedkingdom | Glasgow | 320 | Glasgow City | G2 5AD | spenergynetworks.***** | 1998 | $642,714,774 | 582 | N/A | N/A | N/A |
| 89 | Smartestenergy LIMITED | Unitedkingdom | Stepney | The Columbus Building 7 Westferry Circus | London | E14 4HD | smartestenergy.***** | 2000 | $634,730,637 | 667 | N/A | N/A | N/A |
| 90 | East Anglia One LIMITED | Unitedkingdom | City of London | 3 Level | London | EC4Y 0AH | N/A | 2010 | $626,956,805 | 4 | N/A | N/A | N/A |
| 91 | Drax Smart Generation Holdco LIMITED | Unitedkingdom | Selby | Drax Power Station | North Yorkshire | YO8 8PH | N/A | 2011 | $615,127,478 | 298 | N/A | N/A | N/A |
| 92 | Medway Power LIMITED | Unitedkingdom | Reading | 43 Forbury Road | Reading | RG1 3JH | N/A | 1990 | $597,878,192 | 45 | N/A | N/A | N/A |
| 93 | Cedar Energy And Infrastructure LIMITED | Unitedkingdom | Moorgate | 33 Holborn | London | EC1N 2HT | N/A | 2019 | $593,992,748 | 294 | N/A | N/A | N/A |
| 94 | Ecotricity LIMITED | Unitedkingdom | Stroud | Lion House | Gloucestershire | GL5 3BY | ecotricity.***** | 1995 | $577,962,986 | 383 | N/A | N/A | N/A |
| 95 | Northern Ireland Electricity Networks LIMITED | Unitedkingdom | Malone Upper | P O Box 2 | Belfast | BT9 5HT | nienetworks.***** | 1991 | $573,119,032 | 1,578 | N/A | N/A | N/A |
| 96 | Seagreen Holdco 1 LIMITED | Unitedkingdom | Reading | No.1 Forbury Place | Reading | RG1 3JH | N/A | 2010 | $570,338,483 | 331 | N/A | N/A | N/A |
| 97 | Seagreen Wind Energy LIMITED | Unitedkingdom | Reading | No 1 Forbury Place | Reading | RG1 3JH | energis.***** | 2009 | $570,211,572 | 337 | N/A | N/A | N/A |
| 98 | Scottish Hydro Electric Power Distribution PLC | Unitedkingdom | Buchanty | Inveralmond House | Perth and Kinross | PH1 3AQ | ssen.***** | 2000 | $560,008,860 | 1,842 | N/A | N/A | N/A |
| 99 | Smartestenergy Business LIMITED | Unitedkingdom | Worthing | Ridgeworth House | West Sussex | BN11 1RY | smartestenergy.***** | 2008 | $548,648,296 | 146 | N/A | N/A | N/A |
| 100 | Axpo UK LIMITED | Unitedkingdom | Moorgate | 155 Fenchurch Street | London | EC3M 6AL | axpo.***** | 2008 | $540,592,127 | 35 | N/A | N/A | N/A |