| LOW Nabs Ltd | Grange-Over-Sands | 2014 |
| LOW Price Energy Ltd | London | 2019 |
| LOW Spinney Wind Farm Limited | London | 2010 |
| LOW Waterhead Limited | Elgin | 2013 |
| Lower Basset Down PV Limited | Saffron Walden | 2014 |
| Lower Coalmoor Bess Ltd | London | 2022 |
| Lower Drayton Biogas Investco Limited | Stokesley | 2019 |
| Lower Easton Solar C.I.C. | Radstock | 2015 |
| Lower END Farm Solar Park Limited | Bristol | 2013 |
| Lower Farm Renewable Energy Limited | Reading | 2025 |
| Lower Farm Solar and Battery Storage Limited | Birmingham | 2022 |
| Lower Frankton Bess Limited | Cardiff | 2023 |
| Lower Mays Solar Farm Limited | Bristol | 2020 |
| Lower Minety Energy Limited | Reading | 2018 |
| Lower Ninestones Solar PV Ltd | Wadebridge | 2015 |
| Lower Reule Bioenergy Limited | Ely | 2008 |
| Lower Tean Leys Solar Farm Limited | Bristol | 2020 |
| Lower Wyke Farm Solar Park Limited | Shepton Mallet | 2020 |
| Lowerfield Energy Centre Limited | Norwich | 2022 |
| Lowfield Energy Centre Limited | Essex | 2021 |
| Lowther Renewables Ltd | Ross-On-Wye | 2019 |
| Lowwood Products Company Limited(The) | Ulverston | 1953 |
| Loxley Plantation Solar Ltd | Rugeley | 2024 |
| LPF Energy Limited | Wrexham | 2022 |
| LPF Kinetica UK Limited | Gatwick | 2015 |
| LPF UK Equityco Limited | Gatwick | 2015 |
| LPF UK Solar Limited | Gatwick | 2015 |
| LPG GAS Coventry Limited | Coventry | 2025 |
| LPG Switch Limited | Clevedon | 2025 |
| Lpgas 4 Wales Limited | Ammanford | 2013 |
| LPU Wind Ltd | Liverpool | 2025 |
| LRC Renewables Ltd | Dundee | 2026 |
| LRO Energy Ventures Limited | Torquay | 2025 |
| LT AC Ltd | Basildon | 2023 |
| LTB Utilities Limited | Sittingbourne | 2026 |
| LTH Utilities Ltd | Ware | 2019 |
| LTI Reenergy Cleantech Bangladesh Ltd | London | 2019 |
| LTI Reenergy Cleantech Global Ltd | London | 2023 |
| LTI Reenergy Cleantech Guinea Ltd | London | 2020 |
| LTI Reenergy Cleantech Industries Ltd | London | 2024 |
| LTI Reenergy Cleantech Investments Ltd | London | 2020 |
| LTI Reenergy Cleantech Nigeria Ltd | London | 2020 |
| LTI Reenergy Cleantech Solar Ltd | London | 2023 |
| LTI Reenergy Cleantech Uganda Ltd | London | 2023 |
| Ltmr Investments Limited | London | 2021 |
| LTS Climate Ltd | Cockfosters | 2025 |
| Lucchini Homes Ltd | London | 2021 |
| Lucena Ltd | Sheffield | 2018 |
| Lucern Solar C.I.C. | Redditch | 2015 |
| Lucid Power Group Limited | London | 2024 |
| Ludevit Tradings Ltd | Manchester | 2016 |
| Ludlow BIO Energy Ltd | Liverpool | 2013 |
| Lugano Solar Limited | London | 2022 |
| Luing Holdings Limited | Oban | 2020 |
| Luke Grey Electrics Limited | London | 2019 |
| Lukemans Limited | Peterborough | 2017 |
| Lullington Power Limited | Frome | 2007 |
| Lumar Electrical Services Ltd | London | 2004 |
| Lumby Energy Storage Park Limited | London | 2023 |
| Lumen Energy Limited | London | 2014 |
| Lumetric Energy Technologies Ltd | Romford | 2025 |
| Lumetrix Energy Limited | Attleborough | 2025 |
| Lumina Metals and Energy Ltd | Barnet | 2025 |
| Lumina Solar Energy Solutions Limited | Rhyl | 2025 |
| Lumina Solarworks Ltd | Bedford | 2025 |
| Luminabatt Ltd | Edinburgh | 2025 |
| Luminance Solar Limited | London | 2012 |
| Luminar Energy Investment and Trading Ltd | Sevenoaks | 2026 |
| Luminasset Ltd | London | 2026 |
| Luminex Power Limited | Barnet | 2025 |
| Luminous Energy (CA) Limited | London | 2014 |
| Luminous Energy (CM) Limited | Corsham | 2025 |
| Luminous Energy (EF) Limited | Corsham | 2016 |
| Luminous Energy (RH) Limited | Reading | 2021 |
| Luminous Energy Generation Limited | Corsham | 2023 |
| Luminous Energy UK Limited | Corsham | 2023 |
| Lumis Energy Ltd | Brighton | 2026 |
| Lumivera Green Energy Ltd | London | 2026 |
| Lumley Solar Limited | London | 2021 |
| Lumos Renewables Ltd | Paisley | 2023 |
| Lumsdaine Renewables Limited | Eyemouth | 2012 |
| Lun's Fithub Limited | Glasgow | 2023 |
| Luna Power Ltd | Bideford | 2023 |
| Lunanhead Energy Storage Limited | London | 2020 |
| Lunanhead Renewables Limited | Shepton Mallet | 2025 |
| Lunar Developments INT Ltd | Tonbridge | 2021 |
| Lundy View Estates Limited | Bodmin | 2011 |
| Lupe Connect Ltd | London | 2024 |
| Lurg Hill Wind Farm Limited | Edinburgh | 2014 |
| Lurgan Road Energy Ltd | Crumlin | 2026 |
| Lurganmore Wind Farm Limited | Cookstown | 2021 |
| Luscott Barton Solar Limited | Faversham | 2012 |
| Luton HOO Estate Electricity Limited | Luton | 2015 |
| Lutterworth Renewable Energy Limited | Reading | 2024 |
| LUX Energy Limited | London | 2009 |
| LUX Plumbing & GAS Ltd | Bradford | 2022 |
| Luxaircons Ltd | London | 2026 |
| Luxe AC Ltd | Sittingbourne | 2025 |
| Luxion Renewables Limited | Eastleigh | 2024 |
| Luxsit Energy Solutions Ltd | London | 2021 |