| Epping Energy Park Limited | London | 2022 |
| EPR EYE Limited | London | 1988 |
| Epsilon Europa Ltd | London | 2024 |
| EQ Electrics Ltd | Dunstable | 2021 |
| Equans FM Limited | Newcastle Upon Tyne | 1960 |
| Equator Solar Limited | Manchester | 2024 |
| Equinicity Ltd | Cheltenham | 2018 |
| Equinor Blandford Road Limited | London | 2019 |
| Equinor Celtic Sea PDA3 Holdco Limited | London | 2021 |
| Equinor Celtic Sea PDA3 Limited | London | 2025 |
| Equinor Welkin Mill Limited | London | 2018 |
| Equinox Electrical Ltd | Livingston | 2014 |
| Equitix Collacott Holdco Limited | London | 2016 |
| Equitix Debdale Holdco Limited | London | 2016 |
| Equitix ESI CHP (Wrexham) Limited | Rockcliffe | 2016 |
| Equitix Handley Park Holdco Limited | London | 2016 |
| Equitix Kessingland Limited | Nottingham | 2007 |
| Equitix Stretton Holdco Limited | London | 2016 |
| Equitix Wern DDU Limited | Nottingham | 2002 |
| Equitix Wind Co 1 Limited | London | 2016 |
| Equitix Wind Co 3 Limited | London | 2018 |
| Equity Eco Services Ltd | Shepperton | 2026 |
| Equo Energy Company Limited | Holywood | 2015 |
| ER Corporate Ventures Ltd | Marlborough | 2022 |
| ER New Projects 1 Limited | Marlborough | 2023 |
| ER New Projects 2 Limited | Marlborough | 2024 |
| ER New Projects 3 Limited | Marlborough | 2026 |
| ER Project Development Co Limited | Marlborough | 2022 |
| Eratec Ltd | London | 2025 |
| Erda Energy Limited | London | 2015 |
| ERE Developments Limited | Derry | 2010 |
| Ergo Energy Ltd | Selkirk | 2014 |
| Erinzen Limited | Waltham Cross | 2020 |
| Erne Renewables Ltd | Derrylin | 2026 |
| Erne Wind Limited | Enniskillen | 2015 |
| Ernesettle Community Solar Limited | Plymouth | 2015 |
| Ernest Air-Cooling Ltd | Shoreham-By-Sea | 2011 |
| Ernie Ellis E + I Services Ltd | Cleethorpes | 2019 |
| Errigal Energy Limited | Belfast | 2012 |
| Erris Powerlines Ltd | Crumlin | 2014 |
| Erskine Generation Limited | Greenock | 2017 |
| ES Realisations Limited | Sale | 2015 |
| ESB (Coalburn 2) Ltd | Perth | 2025 |
| ESB (Coalburn) Ltd | Perth | 2024 |
| ESB (Harker) Ltd | Perth | 2024 |
| ESB (Scotland) Ltd | Perth | 2023 |
| ESB Asset Development UK Limited | London | 2009 |
| ESB Energy Limited | London | 2015 |
| ESB Group (UK) Limited | London | 2001 |
| ESB Solar (Northern Ireland) Limited | Derry | 2015 |
| Esbni Limited | Londonderry | 2010 |
| Escart Windfarm Ltd | Stonehouse | 2025 |
| ESD Air Conditioning Limited | Dukinfield | 2025 |
| ESF Llwyndu Limited | London | 2013 |
| ESG Local Projects Limited | Preston | 2022 |
| Esgair Galed Energy Park Limited | Cardiff | 2021 |
| Eska Energy Limited | Omagh | 2022 |
| Eskdalemuir Wind Farm Limited | Wrexham | 2007 |
| ESL 001 Limited | London | 2021 |
| ESL 002 Limited | London | 2021 |
| Esla Consulting Ltd | Leamington Spa | 2021 |
| ESP Electrical Ltd | Staffordshire | 2000 |
| ESP Electricity Limited | Leatherhead | 2003 |
| ESP Heat Limited | Leatherhead | 2026 |
| ESP Idno Limited | Leatherhead | 2026 |
| ESS (Berkshire) Limited | Ascot | 2017 |
| ESS Ireland Ltd | Belfast | 2024 |
| ESS Ltd | Derby | 2021 |
| Essential Mechanical Solutions Ltd | Orpington | 2016 |
| Essentially Energy Limited | Doncaster | 2025 |
| Essex Air Conditioning & Refrigeration Services Limited | Benfleet | 2014 |
| Essex Community Energy CIC | Polegate | 2022 |
| Essex Electrical & Air Conditioning Ltd | Basildon | 2019 |
| Essex Vehicle Charging Ltd | Colchester | 2021 |
| Esss Limited | Stafford | 2017 |
| Established Energy Solutions Limited | Maldon | 2020 |
| Estio Solar Limited | London | 2012 |
| Estrans Developments (Severn Beach) Limited | London | 2015 |
| Estuary Commercial Utilities Ltd | Caldicot | 2021 |
| Estuary Energy Ltd | Caldicot | 2021 |
| ET Biogas Ventures Limited | Rugeley | 2013 |
| Etavi Renewables Limited | London | 2022 |
| Eternal NRG Limited | Cheadle | 2025 |
| Eternity Fire and Security Ltd | Swansea | 2022 |
| Etgas Burnley Limited | Fleetwood | 2023 |
| Ethical Energy (UK) Ltd | Swansea | 2011 |
| Ethical Energy Developments Ltd | St. Austell | 2012 |
| Ethical Power O&M Limited | Exeter | 2023 |
| Ethical Shelf Limited | Exeter | 2023 |
| Ethos Green Energy Ltd | Faversham | 2023 |
| Ethtry Energy Limited | Esher | 2026 |
| Eticauk Ltd | Manchester | 2026 |
| Etive Gridco Ltd | Perth | 2014 |
| ETS Consulting & Global Trading, Ltd | London | 2019 |
| EU Solar Power Ltd | Limavady | 2025 |
| Eugeneious Solar Limited | London | 2025 |
| Euro Buying Service Limited | Dartford | 2015 |
| Euro Enerji A.S Ltd | Milton Keynes | 2024 |
| Euro Link Industrial Ltd | Leeds | 2026 |
| Eurocool Limited | Peterborough | 2013 |