| Field Walham Ltd | London | 2024 |
| Field Whitebirk Ltd | London | 2017 |
| Field Woodhead Ltd | London | 2025 |
| Field Yaxley Ltd | London | 2024 |
| Fields 9,10,11 Limited | Ely | 2013 |
| Fields Farm Solar Limited | London | 2014 |
| Fife's Electrical Services Limited | Kendal | 2008 |
| Fifty Wind Co 1 Limited | Godalming | 2019 |
| Figure of Eight Events Limited | Leeds | 2013 |
| FIM Electrical Ltd | Fortrose | 2026 |
| FIM Windfarms (SC) General Partner Limited | Edinburgh | 2007 |
| Finch Business Consultant Ltd | London | 2022 |
| Finch Electrical Distribution Limited | London | 2018 |
| Findhorn Wind Park Limited | Forres | 2002 |
| Findlay Electrical Limited | Romford | 2017 |
| Finfoot Energy Limited | London | 2017 |
| Fingal Wind Limited | Lancaster | 2014 |
| Finish Electrical Limited | Torquay | 2015 |
| Finlight DG UK Ltd | Bristol | 2023 |
| Finroc Ltd | London | 2023 |
| Fintry Community Energy Limited | Glasgow | 2014 |
| Fintry Renewable Energy Enterprise | Glasgow | 2005 |
| Finvoy Solar Limited | London | 2013 |
| Fiord Wind Ltd | Newtownards | 2016 |
| Firelec (Bournemouth) Ltd | Ferndown | 2004 |
| Fireman 112 Ltd | Morden | 2019 |
| Firgreen Energyfarm Limited | Sunderland | 2024 |
| Firma Energy AP Ltd | Ripon | 2025 |
| Firma Energy DM Ltd | Ripon | 2023 |
| Firma Energy MF Ltd | Ripon | 2023 |
| Firma Energy WF Ltd | Ripon | 2023 |
| Firmus Energy (Supply) Limited | London | 2005 |
| Firs Farm Turbine Limited | Fareham | 2014 |
| Firsfield Solar Limited | Rugby | 2022 |
| First Call Plumbing and Heating Ltd | Stoke-On-Trent | 2024 |
| First Central Heating Company Limited | Carlisle | 2015 |
| First Choice Air Conditioning Limited | Sheffield | 2017 |
| First Choice Renewables Ltd | Sunderland | 2019 |
| First Choice Utilities Ltd | London | 2018 |
| First Energy Limited | Cheltenham | 2010 |
| First Hvac Solutions Ltd | London | 2023 |
| First Hydro Company | Gwynedd | 1989 |
| First Milk Energy Limited | Glasgow | 2012 |
| First Onsite Electrical Limited | London | 2021 |
| First Renewable PSI Limited | London | 2015 |
| First Response Electrical Installations Ltd | Darlington | 2014 |
| First Utility Limited | Manchester | 2004 |
| First Wind Limited | Queens Island | 2012 |
| Firthside Limited | Ayrshire | 2021 |
| Fisair UK Ltd | Louth | 2019 |
| Fischer Limited | Manchester | 2025 |
| Fish Pond Ring Ltd | Tetbury | 2014 |
| Fishburn Solar Limited | Edinburgh | 2021 |
| Fishcross Generation Limited | Greenock | 2018 |
| Fisherplace Hydro Limited | London Colney, St. Albans | 2015 |
| Fishpond Energy Limited | Exeter | 2015 |
| Fishwind Acquisition Limited | London | 2018 |
| Fishwind Limited | London | 2018 |
| Fitz Energy Limited | Newtownards | 2013 |
| Fitzpatrick Energy Limited | Newry | 2014 |
| Five Lanes Solar Limited | Liverpool | 2020 |
| Five Mile Drive Holdings Limited | Milton Keynes | 2015 |
| Five Mile Drive Solar Park Limited | Milton Keynes | 2013 |
| Five Oaks Solar Farm Limited | Hove | 2014 |
| Five Oaks Solar Park Limited | London | 2010 |
| Five Points Windfarm Limited | Enniskillen | 2015 |
| FIX IT Electrical Solutions Ltd | Rochdale | 2023 |
| Fixon & Bailey Ltd | Slough | 2024 |
| Fizz Energy Ltd | London | 2023 |
| FJE Electrical Services Limited | Tonbridge | 2017 |
| FJM Electrical Services Ltd | Leyland | 2016 |
| Flair Energy Limited | Bradford | 2012 |
| Flamecare (Powys) Limited | Newtown | 2007 |
| Flamefx Ltd | Hemel Hempstead | 2007 |
| Flameless Energy Systems Limited | Brentford | 2014 |
| Flamewise Ltd | Cardiff | 2016 |
| Flare AIR2AIR Ltd | Sandy | 2026 |
| Flash Electrical Solution Ltd | Chelmsford | 2019 |
| Flash M&E Ltd | London | 2016 |
| Flawborough Farms Ltd | Nottingham | 2023 |
| Flaxetta Limited | Strabane | 2025 |
| Flaxlands Solar Farm Limited | London | 2024 |
| Fleet Green Limited | London | 2020 |
| Fleet Hampshire Energy Limited | London | 2023 |
| Fleetsolve Limited | Wirral | 2002 |
| Fleetwood WTE Limited | London | 2018 |
| Flemington Solar Ltd | Ross-On-Wye | 2024 |
| Flex Hill Ltd | Caithness | 2005 |
| Flex-Go Energy Limited | Hayes | 2023 |
| Flexi Bill Limited | London | 2016 |
| Flexible Energy Limited | Weymouth | 2022 |
| FLEXIBLEGRIDPOWER3 Ltd | Warrington | 2017 |
| Flexion Energy SPV 1 Ltd | London | 2022 |
| Flexion Energy SPV 2 Ltd | London | 2022 |
| Flexion Energy SPV 3 Ltd | London | 2023 |
| Flexion Energy SPV 4 Ltd | London | 2023 |
| Flexion Energy SPV 5 Ltd | London | 2023 |
| Flexion Energy SPV 6 Ltd | London | 2023 |
| Flexion Energy SPV 7 Ltd | London | 2023 |
| Flexion Energy SPV 8 Ltd | London | 2023 |