| Four Seasons AC Services Ltd | Birmingham | 2024 |
| Four Seasons Air Conditioning Supplies Limited | West Midlands | 1984 |
| Four Two Three Ltd | London | 2024 |
| Fourenergy Installations Ltd | Wrexham | 2024 |
| Fowl Farm Energy Centre Limited | Norwich | 2023 |
| FOX 2023 Limited | Tamworth | 2023 |
| FOX Air Conditioning Limited | Cardiff | 2023 |
| FOX Cover Renewable Energy Limited | Reading | 2023 |
| FOX Covert Solar Farm Limited | London | 2020 |
| FOX Electrical Install Limited | Loughton | 2015 |
| FOX Renewables Limited | Wigan | 2013 |
| Foxash Limited | Bourne End | 2011 |
| Foxburrow Farm Solar Farm Limited | London | 2013 |
| Foxglove Energy Supply Ltd | Leicester | 2015 |
| Foxholes Energy Ltd | Shrewsbury | 2019 |
| Foydragh Wind Ltd | Belfast | 2015 |
| FP Electric Ltd | Banbury | 2022 |
| FP LUX Reio PV Steeraway Limited | Reading | 2021 |
| FP LUX Scurf Dyke Solar Limited | Milton Keynes | 2019 |
| FPK Utilities Limited | Chelmsford | 2018 |
| Fraddon Biogas Limited | Wellingborough | 2013 |
| Fraisthorpe Wind Farm Ltd | London | 2011 |
| Franensa UK Limited | London | 2026 |
| Franklin EV Limited | Wilmslow | 2015 |
| Fraserburgh Energy Ltd | London | 2021 |
| Freasdail Energy Limited | Kings Langley | 2015 |
| Freathy Solar Park Limited | Gatwick | 2013 |
| Fred. Olsen Limited | London | 1963 |
| Fredoch Limited | Pencaitland | 2013 |
| Free Energy Help Ltd | Derby | 2025 |
| Free Green Energy Corporation (Solar) Limited | Norwich | 2015 |
| Free Green Energy Corporation Limited | Norwich | 2010 |
| Freeair Services Limited | Southampton | 2005 |
| Freeby Lane Green Energy Park Limited | London | 2023 |
| Freedom Corporation Ltd | London | 2024 |
| Freehand HQ Limited | London | 2024 |
| Freelance Inspection Testing Limited | Walsall | 2014 |
| Freetricity Commercial Ltd | London | 2010 |
| Freetricity Limited | London | 2010 |
| Freetricity Operations Ltd | London | 2010 |
| Freetricity Solar Assets Company Limited | London | 2011 |
| Freetricity South East Limited | London | 2011 |
| Freewatt (Solar 4) Ltd | Lincoln | 2023 |
| Freeway Business Solutions Limited | Bristol | 2022 |
| French Farm Limited | Kings Langley | 2010 |
| Frenich Hydro Limited | Edinburgh | 2010 |
| Freon Supply Limited | Deeside | 2025 |
| Fresco Energy Limited | Evesham | 2018 |
| Fresh Air Facilities Limited | Dartford | 2026 |
| Fresh Air Solutions Limited | Dartford | 2025 |
| Fresh Business Utilities Limited | Spennymoor | 2024 |
| Fresh Energy Limited | Manchester | 2018 |
| Fresh Green Power Limited | London | 2011 |
| Fresh Ventilation Ltd | Carrickfergus | 2019 |
| Freshview Energy Ltd | Wantage | 2022 |
| Freshwayz Ltd | Solihull | 2025 |
| Friction Energy Ltd | Dartford | 2020 |
| Fridge Village Ltd | London | 2019 |
| Frocester Solar Farm Limited | Cheltenham | 2022 |
| Frodsham Green Power Ltd | Ross-On-Wye | 2023 |
| Frodsham Solar Holdco Limited | London | 2022 |
| Frodsham Solar Limited | London | 2022 |
| Frodsham Wind Farm Limited | London | 2009 |
| Frog Lane Energy Storage Limited | Shepton Mallet | 2023 |
| Froghall Energy Limited | Rugeley | 2023 |
| Frogs Loke Solar Ltd | Gatwick | 2015 |
| Frome Solar Limited | London | 2013 |
| Frome Valley Solar Farm Holdco Limited | Reading | 2024 |
| Frome Valley Solar Farm Limited | Reading | 2024 |
| Frontier Energy Ltd | Buckfastleigh | 2022 |
| Frontier Power Energy Holdings Limited | London | 2025 |
| Frontier Power Limited | Warwick | 2009 |
| Frontier Power Management Services Limited | Warwick | 2025 |
| Frontier Power Services Limited | Warwick | 2009 |
| Frontier Power Storage Holdings Limited | London | 2025 |
| Frontier Power Ventures Holdco Limited | Warwick | 2025 |
| Frost Air Solutions Ltd | Felpham | 2011 |
| Frost Design Associates Limited | Lytham St. Annes | 2003 |
| Frost Flow Ltd | London | 2026 |
| Frost Guardian Hvac Ltd | Northampton | 2023 |
| Frostrow Limited | Norwich | 2019 |
| Frosty FIX Ltd | Luton | 2025 |
| FRP Mercia Holdco 2 Limited | Nottingham | 2020 |
| FRP Mercia Holdco 3 Limited | Nottingham | 2021 |
| FRS Air Conditioning Ltd | Tring | 2024 |
| FRV Powertek Limited | London | 2022 |
| FRV Services Energy UK Limited | Reading | 2022 |
| FRV Tyler Hill Bess 1 Limited | London | 2022 |
| FRV Tyler Hill Bess 2 Limited | London | 2022 |
| Fry's Electrical Limited | Bournemouth | 1985 |
| Fryingdown Solar Park Limited | London | 2010 |
| FS Ford Farm Solar 1 Limited | London | 2013 |
| FS West Gourdie Limited | London | 2019 |
| Fsavu Limited | West Malling | 2018 |
| Fswind Limited | Witney | 2010 |
| FTI Renewable Energy Systems Ltd | Leamington Spa | 2025 |
| FTS Energy Limited | Rowley Regis | 2011 |
| Fu-Gen Energy UK Limited | Norwich | 2022 |
| Fuel Systems UK Ltd | Rotherham | 2009 |
| Fulcrum Electricity Assets Limited | Sheffield | 2012 |