| LDF Air Solutions Ltd | Gravesend | 2019 |
| LDG Ltd | Spennymoor | 2021 |
| LDM Contracts Limited | Glasgow | 2023 |
| LDN Utilities Ltd | Welwyn Garden City | 2019 |
| LDP Solar Ltd | London | 2024 |
| LDS Air Conditioning Services Ltd | London | 2018 |
| LDS Construction Ltd | Stafford | 2023 |
| LDS15 WAG Consultants Ltd | Leeds | 2025 |
| LE Solar 51 Limited | London | 2016 |
| Le-Hair Plumbing & Heating Limited | Newark | 2023 |
| LE20 Limited | Birmingham | 2015 |
| LEA Hall Energy Limited | Shrewsbury | 2015 |
| Leacann Electric Company Limited | London | 2014 |
| Leach Hvac Ltd | Spilsby | 2014 |
| Leader Air Conditioning Limited | Ashton | 1986 |
| Leadgen Hub Limited | Waterlooville | 2025 |
| Leading Electrical Solutions Ltd | Edinburgh | 2019 |
| Leaf Energy Ltd | Preston | 2021 |
| Leafield Energy Limited | Winchester | 2015 |
| Leaford Energy Limited | Kings Langley | 2024 |
| Leam Turbines Limited | Tempo | 2014 |
| Leamington Dog Fields Limited | Leamington Spa | 2016 |
| Lean Carbon Limited | Bedford | 2016 |
| Leap 24 UK Limited | London | 2021 |
| Learanaich Wind Farm Limited | London | 2023 |
| Leatherhead Bess Ltd | London | 2022 |
| Lebgas Gas&Heatingservices Limited | Chatham | 2017 |
| LEC Catering Limited | London | 2024 |
| Ledwyche Solar Limited | Edinburgh | 2021 |
| LEE Cooling Ltd | Worthing | 2022 |
| LEE D B Electrical Ltd | Middlesbrough | 2015 |
| Leeds Aircon Solution Ltd | Batley | 2023 |
| Leeds Rewire Services Ltd | Leeds | 2025 |
| Leeming Solar Farm Limited | London | 2020 |
| Leep Electricity Networks Limited | Manchester | 2008 |
| Leep Electricity Services Limited | Manchester | 2008 |
| Leep GAS Networks Limited | Manchester | 2017 |
| Leep Utilities Consultancy Limited | Manchester | 2006 |
| Leep Utilities Services Limited | Manchester | 2006 |
| Leesrigg Renewables Limited | Cockermouth | 2014 |
| Legacy Air Conditioning Installations Limited | Waterlooville | 2025 |
| Legacy Air Conditioning Services Limited | Waterlooville | 2023 |
| Legacy Air Services Ltd | London | 2023 |
| Legacy Green Energy Limited | Faversham | 2021 |
| Legacy NG Limited | Cheltenham | 2024 |
| Legacy Pipework & Welding Ltd | Derby | 2025 |
| Legananny Renewables Ltd | Banbridge | 2013 |
| Legavallon Wind Limited | Belfast | 2019 |
| Leicester District Energy Company Limited | London | 2006 |
| Leicestershire Solar 1 Limited | Windsor | 2020 |
| Leiper Windpower Limited | Morpeth | 2014 |
| Leirum Energy Limited | Belfast | 2016 |
| Leisuregaz Limited | Eccles | 2013 |
| Leith Energy Limited | London | 2023 |
| Leithenwater Wind Energy Hub Limited | Bristol | 2021 |
| LEL Bilbo Battery Limited | London | 2022 |
| LEL Bilbo Solar II Limited | London | 2022 |
| LEL Energy Limited | Liverpool | 2024 |
| LEL Frodo Battery Limited | London | 2022 |
| LEL Frodo Solar & Battery Limited | London | 2019 |
| LEL Twitch Hill Limited | London | 2023 |
| Lemax NDT Ltd | Newton Aycliffe | 2025 |
| Lemnos Energy Ltd | London | 2024 |
| Lemon Lime Energy Limited | Sevenoaks | 2023 |
| Lendrum Energy Limited | Edinburgh | 2024 |
| Lendrum's Bridge Wind Farm Limited | Millbrook | 1998 |
| Lendrums Bridge Energy Limited | Kings Langley | 2024 |
| Lenex Limited | Northamptonshire | 2015 |
| Lenham Solar Limited | London | 2010 |
| Leni Solar Limited | London | 2014 |
| Lennon Electrical Limited | Hyde | 2017 |
| Lenston Ltd | Morpeth | 2026 |
| LEO1B Energy Park Limited | Bristol | 2023 |
| Leolite (Scunthorpe) Limited | London | 2014 |
| Leominster Air CON Limited | Ludlow | 2025 |
| Leonardo Capital Ltd | London | 2025 |
| Lepetomane Limited | London | 2014 |
| Lepg Services Ltd | Birmingham | 2015 |
| Lerna Bess Limited | Bristol | 2022 |
| Lesath Solar Limited | Bristol | 2023 |
| Lesserlinn Windpower Limited | Lanark | 2012 |
| Lethans East Wind Farm Limited | Houghton-Le-Spring | 2012 |
| Lethans Wind Farm Limited | Houghton-Le-Spring | 2012 |
| Lets Go Solar Ltd | Cambridge | 2022 |
| Letserve Ltd | Walsham-Le-Willows | 2021 |
| Leuchland Energy Centre Limited | Norwich | 2024 |
| Lev-Testing-Uk Ltd | Bury | 2024 |
| Level-Line Limited | West Wickham | 2003 |
| Leven Generation Limited | Greenock | 2017 |
| Leven Power Limited | Northampton Business Park | 2005 |
| Levenseat Renewable Energy Holdings Limited | Edinburgh | 2015 |
| Levenseat Renewable Energy Ltd | Edinburgh | 2014 |
| Levenside Bess Ltd | London | 2022 |
| Leveret Land Limited | Paisley | 2012 |
| Levington Energy Limited | Yarm | 2017 |
| Lewisford Electrical Ltd | Wallington | 2015 |
| Lewisham Esco Limited | Blackburn | 2023 |
| Lewtas Electrical Limited | Manchester | 2022 |
| Lexo Electric Ltd | Salsburgh | 2024 |
| Leyland Metering Services Limited | London | 2016 |