| Lady Wood Solar Farm Limited | Aylesbury | 2023 |
| Ladyburn Wind Farm Limited | Glasgow | 2011 |
| Ladyfield Renewable Energy Park Ltd | Chipping Norton | 2021 |
| Lagan Energy (Antrim) Limited | Belfast | 2022 |
| Lagan Energy (Ballymena) Limited | Belfast | 2021 |
| Lagan Energy (Ballyvallagh) Limited | Belfast | 2021 |
| Lagan Energy (Lurgan) Limited | Belfast | 2021 |
| Laggan Hydro Limited | Edinburgh | 2019 |
| Laggan Wind Farm Limited | London | 2024 |
| Lagness Solar Farm Limited | Exeter | 2014 |
| Lains Farm Solar Limited | Birmingham | 2020 |
| Lairdmannoch Energy Park Limited | Edinburgh | 2021 |
| Lairg Windfarm Limited | Edinburgh | 2005 |
| Lake District Biogas Limited | Glasgow | 2014 |
| Lake Electrical Limited | Hailsham | 2008 |
| Lakeside Energy Storage Limited | Kings Langley | 2017 |
| Lakeview Energy Ltd | Armagh | 2024 |
| Lambeg Energy Limited | Lisburn | 2025 |
| Lambert Heating Services Ltd | Rochester | 2020 |
| Lambridge Solar Limited | London | 2013 |
| Lambriggan Energy Ltd | Perranporth | 2012 |
| Lambro Refrigeration Ltd | Colchester | 2002 |
| Lambs Hill Wind Farm Limited | London | 2009 |
| LAN Fawr Energy Park Limited | Cardiff | 2020 |
| Lana Term Ltd | Kington | 2025 |
| Lancaster Power 2 Ltd | London | 2024 |
| Lancaster Power Limited | London | 2016 |
| Lancaster SD Limited | London | 2015 |
| Lancaster University Energy Services Ltd | Lancaster | 1989 |
| Lanchester Energy Limited | Annfield Plain | 2013 |
| Lanchester Properties Limited | Annfield Plain | 1999 |
| Landfill GAS Generation Limited | Larne | 2008 |
| Landhead Power Ltd | Ballymoney | 2012 |
| Landmark Power Ltd | London | 2019 |
| Landmark Private Wires Limited | Cardiff | 2026 |
| Landmark Windpower (Scotland) Ltd | Glasgow | 2024 |
| Landmead Solar Farm Limited | London | 2013 |
| Lands of Glenside Limited | Stirling | 2024 |
| Langage Solar Park Limited | Middlesbrough | 2010 |
| Langar Lane Community Solar CIC | London | 2015 |
| Langcliffe Park Residents Ltd | Swansea | 2013 |
| Langer Lane Solar Farm Limited | Exeter | 2021 |
| Langford Solar Limited | Norwich | 2015 |
| Langhope RIG Wind Farm Limited | London | 1999 |
| Langlands Solar Limited | Gatwick | 2012 |
| Langley Energy Supply Limited | Chorley | 2025 |
| Langstone Harbour Generation Limited | Kirkby Lonsdale | 2024 |
| Lanhide Ltd | Walsall | 2015 |
| Lans Renewables Ltd | Eastbourne | 2026 |
| Lanshaw Moor Wind Farm Limited | Houghton-Le-Spring | 2025 |
| Lantern Engineering and Trading Ltd | Sutton | 2024 |
| Lapwing Energy Limited | Doncaster | 2015 |
| Lapwing FEN II Ltd. | London | 2016 |
| Larchcover Enterprises Limited | Bristol | 2014 |
| Laricis Energy Limited | London | 2017 |
| Larigan Power Limited | Bristol | 2014 |
| Larimin Limited | London | 2012 |
| Lark Connections Limited | Bourne | 2015 |
| Lark Energy Bilsthorpe Limited | London | 2016 |
| Lark GAS Assets Limited | Bourne | 2016 |
| Lark Power Services Limited | Bourne | 2012 |
| Larkfleet Smart Homes Limited | Bourne | 2014 |
| Larne Battery Storage Limited | Lisburn | 2020 |
| Laroch Hydro Limited | Ballachulish | 2016 |
| Lascar Battery Storage Limited | London | 2017 |
| Last Energy UK Ltd | Bristol | 2021 |
| Last Mile Electricity Limited | Glasgow | 2002 |
| Last Mile GAS Limited | Glasgow | 2006 |
| Latent Drive Ltd | Dorchester | 2020 |
| Laughton Lodge Management and Services Company Limited | Lewes | 2012 |
| Laurel Hill Solar Limited | Belfast | 2013 |
| Laurelgreen Energyfarm Limited | Sunderland | 2024 |
| Laurels Farm Renewable Power Limited | Chester | 2021 |
| Lavender Hill Garage Enfield Limited | Middlesex | 2006 |
| Lavery Consultancy Limited | Ballynahinch | 2014 |
| Lawford Solar Ltd | Altrincham | 2022 |
| Lawhill Wind Limited | Forfar | 2014 |
| Lawn Lane Solar Limited | London | 2013 |
| Lawsonsmetering Ltd | Dunstable | 2026 |
| Layer Marney Heating Limited | Wanstead | 2012 |
| Layer One Projects Limited | Milton Keynes | 2010 |
| Layer Solar Farm Limited | London | 2020 |
| Layfield Renewable Ltd | Crook | 2012 |
| Laynes Green Energy Limited | Barnetby | 2015 |
| Layton & Powell Electrical Limited | Hereford | 1998 |
| LC Electrical 96 Limited | Sheffield | 2017 |
| LC Gridworks Ltd | Durham | 2026 |
| LCB Cooling Ltd | Cardiff | 2020 |
| LCC NW Ltd | Ashton-Under-Lyne | 2021 |
| LCC Power Limited | Cookstown | 2011 |
| LCD Installations Ltd | Manchester | 2024 |
| LCG Pipelines Ltd | Bilston | 2018 |
| LCH Renewables Limited | Seaham | 2014 |
| Lchem GAS Supplies Ltd | Pontyclun | 2026 |
| LCIP1 Holdings Limited | London | 2015 |
| Lcmp Limited | Canterbury | 2024 |
| LCR Business Ltd | London | 2023 |
| LCS Cooling Limited | Edenbridge | 2018 |
| LCT Builder Ltd | London | 2022 |
| LCW2E2 Development Limited | London | 2020 |