| Ardnacross Energy Limited | Isle Of Mull | 2013 |
| Ardonald Renewables Limited | Derby | 2024 |
| Ardos Energy Limited | Birmingham | 2016 |
| Ardrishaig Renewable Energies Limited | Tarbert | 2010 |
| Ardrossan Wind Farm (Scotland) Limited | Edinburgh | 2003 |
| Ards Battery Storage Ltd | Belfast | 2021 |
| Ardstraw Energy Ltd | Omagh | 2024 |
| Ardvark Electrical Limited | Hull | 2018 |
| Ardverikie Estate Limited | Newtonmore | 1956 |
| Ardvorlich Estate Limited | Perthshire | 1960 |
| Arena Capital Partners (NI) Limited | Belfast | 2015 |
| Arena Renewables Ltd | Chester | 2021 |
| Arena Wind Markethill Limited | Belfast | 2015 |
| Arenko Pineau Limited | London | 2017 |
| Arenko Suntzu Ltd | London | 2015 |
| Ares Electrical Ltd | Brentwood | 2016 |
| Ares Market Services Limited | Belfast | 2022 |
| Arevalous Power SPV 1 Limited | London | 2012 |
| Arfi BES Limited | London | 2025 |
| Arfi DBS Limited | London | 2025 |
| Arfsolar Ltd | Aylesbury | 2025 |
| Argestes Wind Limited | London | 2013 |
| Arglam Renewables Limited | York | 2013 |
| Argon Utility Infrastructure Ltd | Hitchin | 2021 |
| Argyll and Bute Green Energy Ltd | London | 2003 |
| Argyll Energy Development Ltd | Dunoon | 2023 |
| Argyll Hydro Ltd | Perth | 2015 |
| Argyll Solar Limited | London | 2012 |
| Aria Global Ventures PVT Ltd | London | 2025 |
| Arico Energy AG Limited | London | 2025 |
| Arin Power Limited | London | 2022 |
| Arinna Solar Limited | Mitcham | 2019 |
| Arithmetica Services Limited | London | 2023 |
| ARJ Utilities Ltd | Plymouth | 2021 |
| ARK Bioenergy Limited | London | 2025 |
| ARK Green Renewables Ltd | Carmarthen | 2023 |
| ARK Hill Wind Farm 2 Limited | Biggar | 2021 |
| ARK Hill Wind Farm Limited | Glasgow | 2011 |
| ARK Solar Limited | Market Harborough | 2026 |
| Arka Energy Ltd | London | 2024 |
| Arkaig Hydrogen Plant Limited | Edinburgh | 2023 |
| Arke Engineering Services Limited | Rugby | 2023 |
| Arkha Non-Conventional Energy (Holdings) Limited | Norwich | 2014 |
| ARL 001 Limited | Exeter | 2017 |
| ARL 011 Limited | Manchester | 2017 |
| ARL 016 Limited | London | 2018 |
| ARL 018 Limited | London | 2018 |
| ARL 019 Limited | Ringwood | 2018 |
| ARL 021 Limited | London | 2018 |
| ARL 027 Limited | Exeter | 2018 |
| ARL O09 Limited | Manchester | 2017 |
| Arla Foods Ingredients Felinfach Renewable Energy Limited | Leeds | 2014 |
| Arlec Consulting Limited | Wirral | 2013 |
| Arleston Solar Limited | London | 2024 |
| Arlington Energy Limited | London | 2017 |
| Arlington Infrastructure Limited | Manchester | 2018 |
| ARM Alder Solar Limited | London | 2023 |
| ARM Birch Solar Limited | London | 2023 |
| ARM Cedar Limited | London | 2024 |
| ARM Douglas Solar Limited | London | 2024 |
| ARM Elder Limited | London | 2024 |
| ARM Hawthorn Limited | London | 2025 |
| ARM Maple Limited | London | 2025 |
| ARM Poplar Limited | London | 2025 |
| Armand Electrical Services Ltd Ltd | Watford | 2025 |
| Armer Cabling Limited | Leyland | 2023 |
| Armex Homes Ltd | London | 2025 |
| Armistead Wind Farm Limited | London | 2007 |
| Armitage 18 Solar Limited | Reading | 2021 |
| Armoy Wind Farm Limited | Lisburn | 2022 |
| Armstrong Energy Global Limited | Norwich | 2013 |
| Armstrong Energy Limited | Norwich | 2012 |
| Armstrong Green Energy Ltd | Coleraine | 2013 |
| Armstrong Solar Holdings Limited | Cheltenham | 2013 |
| Armstrong's Farm Limited | Lisburn | 2016 |
| Arnicon Ltd | London | 2025 |
| Arnish Community Windfarm Limited | Stornoway | 2023 |
| Arnish Moor Wind Farm Limited | Preston | 2014 |
| Arnold R & R Limited | Hull | 2014 |
| Aroma Vent International Limited | Hazel Grove | 2024 |
| Arqtic Breeze Ltd | Feltham | 2025 |
| Arran Hydro Limited | Kilmarnock | 2015 |
| Arran View Holding Ltd | Radstock | 2022 |
| Arran View Storage Ltd | Radstock | 2020 |
| Arresgill Energy Limited | Motherwell | 2022 |
| Arresgill Energy Storage 1 Limited | Motherwell | 2023 |
| Arresgill WF Limited | Motherwell | 2022 |
| Arrow Commissioning Ltd | Kent | 2016 |
| Arrow Industrial UK Holding Ltd | Leicester | 2026 |
| Arscott Power Limited | Barnstaple | 2012 |
| Art Electrical Services Ltd | Hayes | 2018 |
| Art Renovation Ltd | London | 2008 |
| Artech Air Limited | Salisbury | 2023 |
| Artel Facilities Management Limited | Stansted | 2015 |
| Artemis FM Ltd | Pevensey | 2021 |
| Artesian Air Limited | London | 2016 |
| Artfield Forest Wind Farm Ltd | London | 2019 |
| Arto.Energy Limited | Bury St. Edmunds | 2014 |
| Arven Offshore Wind Farm Hold Co Limited | London | 2022 |
| Arven Offshore Wind Farm Limited | London | 2022 |