| Arven South Holdings Limited | London | 2022 |
| Arven South Limited | London | 2022 |
| Arvense Limited | Wimborne | 2019 |
| AS Energy Marketing Limited | Stockport | 2023 |
| Asaltern Limited | Wimborne | 2019 |
| ASC Energy PLC | London | 2020 |
| ASC Utility Solutions Limited | Chelmsford | 2020 |
| Asca International Limited | Solihull | 2005 |
| Ascott Estate Solar Limited | Cheltenham | 2023 |
| ASD Renewables Limited | Harlow | 2019 |
| ASE UK Community Solar I Limited | London | 2023 |
| ASE UK Community Solar II Limited | London | 2025 |
| ASE UK Holdings Limited | London | 2021 |
| Asgard Renewables Limited | Haverfordwest | 2013 |
| ASH Plumbing Heating Work Limited | Northolt | 2023 |
| ASH Renewables Limited | Belfast | 2012 |
| ASH Renewables NO 3 Limited | Belfast | 2014 |
| ASH Renewables NO 4 Limited | Belfast | 2014 |
| ASH Renewables NO 5 Limited | Belfast | 2014 |
| ASH Renewables NO 6 Limited | Belfast | 2014 |
| ASH Solar Farm Limited | Derby | 2021 |
| ASH Solar Limited | London | 2014 |
| ASH Technical Services Limited | Tonbridge | 2004 |
| ASH Tree Solar Park Limited | Shepton Mallett | 2023 |
| ASH Valley Energy Reserve Ltd | Faversham | 2025 |
| Ashbrooke Lane Energy Storage Park Limited | London | 2023 |
| Ashby Farms Power Limited | Daventry | 2013 |
| Ashby Solar Farm Limited | Hove | 2015 |
| Ashday Hall Farm Limited | Halifax | 2014 |
| Ashfield GAS Limited | Nottingham | 2021 |
| Ashfield Power Limited | Tewkesbury | 2011 |
| Ashford Mill Developments Ltd | Matlock | 2008 |
| Ashford Power Ltd | London | 2014 |
| Ashford Refrigeration Services Ltd | Stourbridge | 2000 |
| Ashgreen Energyfarm Limited | Houghton Le Spring | 2016 |
| Ashington Renewables Ltd | Clacton-On-Sea | 2024 |
| Ashlawn Solar Limited | Gatwick | 2012 |
| Ashley Todd Electrical Services Ltd | Kings Lynn | 2016 |
| Ashmark Farm Ltd | New Cumnock | 2025 |
| Ashogle Wind Limited | Turriff | 2015 |
| Ashrona Power Systems Limited | West Kilbride | 2007 |
| Ashton Agricultural Waste Plant Holdings Limited | London | 2026 |
| Ashton Agricultural Waste Plant Limited | London | 2026 |
| Ashton Airconditioning Services Limited | Bristol | 2002 |
| Ashton Bentley Renewables Ltd | London | 2019 |
| Ashton Electrical Ltd | Devon | 2006 |
| Ashton Hayes Community Energy C.I.C. | Wrexham | 2011 |
| Ashton Keynes Green Energy Limited | London | 2022 |
| Ashton Power Limited | London | 2016 |
| Ashton Solar Farm Limited | Reading | 2014 |
| Ashwater Solar Limited | West Byfleet | 2014 |
| ASI Engineering UK Limited | London | 2026 |
| Aska Energy (UK) Ltd | Dundee | 2012 |
| Aska Energy Systems Ltd | Kirkwall | 2025 |
| ASM Airconditioning Limited | Wembley | 2012 |
| ASM Power Ltd | London | 2020 |
| Aspect Solar Ltd | London | 2010 |
| Aspen a. C. Ltd | Hailsham | 1987 |
| Aspenone Ltd | Guildford | 2022 |
| Aspire Air Conditioning Solutions Ltd | Leigh | 2013 |
| Aspire Green Ltd | London | 2019 |
| Aspley Battery Storage Limited | Bristol | 2023 |
| Assel Valley Wind Energy Limited | Edinburgh | 2013 |
| Asset-Wise Ltd | Clydebank | 2022 |
| Assura Solaris Limited | Altrincham | 2023 |
| Assured Asset Solar 1 Ltd | London | 2020 |
| Assured Asset Solar 2 Ltd | London | 2020 |
| Assured Solar Ltd | Exeter | 2020 |
| Assured Wind Energy Ltd | Castlewellan | 2020 |
| Assynt Hydro Limited | Lochinver | 1992 |
| Astech Electrical Contractors Limited | Stevenage | 2014 |
| Aster Solar Limited | Devizes | 2015 |
| Astley Solar Limited | Chislehurst | 2014 |
| Aston Grange Solar Limited | Cheltenham | 2022 |
| Aston Lane Solar Farm Limited | Colchester | 2022 |
| Astral Solar Ltd | London | 2010 |
| Astwick Green Power Limited | London | 2022 |
| Astwood Energy Centre Limited | Norwich | 2023 |
| Astwood Energy Reserve Ltd | Faversham | 2026 |
| Astwood Green Energy Ltd | Faversham | 2022 |
| Asuk Holdco 1 Limited | London | 2024 |
| Asuk Holdco 2 Limited | London | 2025 |
| Asuk Holdco 3 Limited | London | 2025 |
| Asuk Holdco 4 Limited | London | 2025 |
| Asuk Holdco 5 Limited | London | 2025 |
| AT Utilites Ltd | Newcastle Upon Tyne | 2023 |
| Atalla Energy Limited | Derry | 2017 |
| ATB Kelpie Wind Limited | Edinburgh | 2016 |
| Ateroll Technology Limited | Felixstowe | 2026 |
| Athena Electrical Limited | London | 1996 |
| Atherstone Solar Farm Ltd | London | 2014 |
| Atholl Hydro Limited | Pitlochry | 2011 |
| Atlantic Green UK Limited | Reading | 2021 |
| Atlantic Hub Energy Limited | Londonderry | 2020 |
| Atlantica Sustainable Infrastructure PLC | London | 2013 |
| Atlantis Cooling Ltd | London | 2020 |
| Atlantis CSP Ltd | London | 2018 |
| Atlantisrealm (West Town) Limited | Elgin | 2012 |
| Atlas Air Group Limited | Glasgow | 2015 |
| Atlas Business Utilities Limited | Enfield | 2024 |