| LMC Electrical Rope Access Ltd | Liverpool | 2024 |
| LMG Systems Solutions Ltd | Troon | 2022 |
| LMG Tech Ltd | Manchester | 2014 |
| LML Utilities Ltd | Manchester | 2023 |
| LMP Electrics Ltd | Leighton Buzzard | 2015 |
| LN Utilities Limited | Chelmsford | 2017 |
| LNG Advisory Services Ltd | London | 2022 |
| LNG Investments Europe Limited | London | 2014 |
| LNG Power Limited | London | 2015 |
| LNH Power Services Ltd | Longfield | 2022 |
| Local Electricians Hertfordshire Ltd | Welwyn Garden City | 2019 |
| Local Air CON Ltd | Camberley | 2026 |
| Local Energy Partnerships Limited | Castleford | 2018 |
| Local Generation Limited | Gainsborough | 2008 |
| Loch Fergus Solar Ltd | Edinburgh | 2022 |
| Loch Kemp Storage Limited | London | 2017 |
| Loch Liath Wind Farm Limited | London | 2020 |
| Loch Luie Ltd | Cumnock | 2014 |
| Lochaber 1 Wind Farm Limited | London | 2023 |
| Lochaber Bess Ltd | Kilwinning | 2024 |
| Lochaber Energy Centre Limited | Essex | 2022 |
| Lochaber Hydro Ltd | Perth | 2015 |
| Lochailort Hydro Limited | Nr Shawbury | 2013 |
| Lochdochart Hydro | Crianlarich | 2006 |
| Lochend Wind Energy Limited | Hamilton | 2013 |
| Lochgoil Energy Limited | Cairndow | 2014 |
| Lochmalony Renewables Limited | Pinner | 2014 |
| Lochore Bess Ltd | Ross-On-Wye | 2023 |
| Lochtower Biogas Limited | Alnwick | 2016 |
| Lochwinnoch Developments Ltd | West Kilbride | 2020 |
| Lockerbie Biogas Limited | Lockerbie | 2018 |
| Locogen Aukera JV Limited | Edinburgh | 2022 |
| Locogen Developments Holdings Limited | Edinburgh | 2022 |
| Locogen Solar Developments Limited | Edinburgh | 2020 |
| Locogen Yieldco Ltd | Edinburgh | 2013 |
| Loddon Power Limited | Bristol | 2016 |
| Lodge Farm Fencing Ltd | Westerham | 2011 |
| Lodge Farm Solar Ltd | London | 2012 |
| Lodge Farm Turbine Ltd | Wadebridge | 2016 |
| Lodge Renewables Limited | Magherafelt | 2011 |
| Lodge Solar Limited | Nottingham | 2013 |
| Logan Energy Limited | Sheffield | 2005 |
| Logan Gill Hydroelectric Ltd | London Colney, St. Albans | 2009 |
| Loganhead WF Limited | Motherwell | 2013 |
| Loganswell Energy Limited | Glasgow | 2022 |
| Loganwood Wind (High Mathernock) Limited | Kilmacolm | 2013 |
| Loganwood Wind Limited | Kilmacolm | 2012 |
| Logic Air Limited | Benfleet | 2020 |
| Logicool Air Conditioning & Heat Pumps Limited | Gallows Hill | 2008 |
| Logie Renewables Limited | Aberdeen | 2014 |
| Logoch Windfarm Ltd | Hamilton | 2011 |
| Lomond Gate EV Ltd | Motherwell | 2025 |
| Lompoc Energy Limited | London | 2017 |
| LON Energy 3 Connection Limited | London | 2020 |
| LON Energy 4 Connection Limited | London | 2021 |
| London & Kent Cable Jointing Limited | Sheerness | 2013 |
| London & Kent Cooling Ltd | Tenterden | 2019 |
| London ACR Ltd | Basildon | 2024 |
| London Air Conditioning Ltd | Borehamwood | 2024 |
| London and Essex Energy Limited | London | 2022 |
| London Arena PLC | London | 2026 |
| London Array Limited | Swindon | 2001 |
| London Cooling Ltd | Sidcup | 2020 |
| London Cooling Services Limited | Oldham | 2021 |
| London Direct Commercial Air Conditioning & Facilities Ltd | Westerham | 2019 |
| London Electricity Ltd | Cardiff | 2017 |
| London LOW Carbon Energy Centre Bess Limited | London | 2022 |
| London Mains Ltd | London | 2022 |
| London Power Limited | London | 2016 |
| London Power Networks PLC | London | 2000 |
| London Power Services Ltd | London | 2025 |
| London Property Certificates Ltd | London | 2018 |
| London Road Energy Centre Limited | London | 2019 |
| London Solar Group Ltd | Chislehurst | 2026 |
| London Southend Solar Limited | Southend-On-Sea | 2014 |
| Londonenergy Ltd | London | 1992 |
| Long ASH Lane Solar Park Limited | Macclesfield | 2015 |
| Long Meadow Solar Farm Limited | London | 2020 |
| Long Newnton Solar Farm Limited | Hove | 2013 |
| Long Newnton Solar Limited | Malmesbury | 2012 |
| Longbreach Solar Farm Limited | London | 2025 |
| Longhedge Solar Limited | Kings Langley | 2022 |
| Longhill Energy Limited | March | 2003 |
| Longlands Solar Farm Limited | London | 2021 |
| Longman Cooling Solutions Ltd | Rotherham | 2025 |
| Longmorn Green Energy Limited | London | 2022 |
| Longner Energy Limited | Shrewsbury | 2012 |
| Longney Solar Limited | London | 2017 |
| Longpasture Solar Farm Limited | Reading | 2020 |
| Longworthy Limited | Wimborne | 2021 |
| Looker Energy Limited | Huntingdon | 2014 |
| Lora Solar Limited | Bristol | 2012 |
| Lordmekaz Limited | Southport | 2016 |
| Lords Meadow Energy Limited | Barnstaple | 2020 |
| Lords Meadow Energy O & M Limited | Barnstaple | 2020 |
| Lorica Energy Limited | London | 2025 |
| Loscar Limited | Kings Langley | 2011 |
| Lostock Power Limited | Rotherham | 2016 |
| Lostock Sustainable Energy Plant Ltd | Rotherham | 2015 |
| Lothian Energy (Scotland) Ltd | Motherwell | 2014 |