| Barguillean Hydro Limited | Edinburgh | 2010 |
| Barkers Holt Wind Farm Limited | Harrogate | 2025 |
| Barking Power Limited | London | 1989 |
| Barkip Biogas Ltd | Buntingford | 2019 |
| Barlborough Limited | Kings Langley | 2012 |
| Barley Brigg Biogas Ltd | Eye | 2014 |
| Barlockhart Moor Wind Energy (Extension) Limited | London | 2012 |
| Barlockhart Moor Wind Energy Limited | London | 2005 |
| Barnacre Solar Limited | London | 2023 |
| Barnes Farm Ltd | Cookstown | 2014 |
| Barnfield Energy Limited | London | 2011 |
| Barnfields Solar Farm Limited | London | 2021 |
| Barnsdale Road Renewables Limited | Shepton Mallet | 2024 |
| Barnsdale Solar Park Limited | Houghton-Le-Spring | 2020 |
| Barnston Estate Solar Ltd | Chester | 2015 |
| Barok Air Conditioning Ltd | Leeds | 2021 |
| Baronagh Ltd | Omagh | 2015 |
| Baronscourt Energy Limited | Newtownstewart | 2011 |
| Barr Cregg Energy Limited | Larne | 2020 |
| Barr Hall Farm Bess Limited | Cheltenham | 2023 |
| Barra and Vatersay Wind Energy Limited | Isle Of Barra | 2010 |
| Barracks Farm Limited | Papplewick | 2012 |
| Barran Caltum Windpower Limited | Argyll | 2012 |
| Barron Wind Limited | Omagh | 2017 |
| Barrow Offshore Wind Limited | London | 2001 |
| Barrow Shipping Limited | Hexham | 2012 |
| Barrs Hydro Ltd | Perth | 2011 |
| Barton Close Farm Solar Park Limited | London | 2012 |
| Barton Solar Bumblebee Limited | Retford | 2023 |
| Barton Solar Gate Burton Limited | Retford | 2023 |
| Bartypower Ltd | Ammanford | 2023 |
| Barvills Solar Farm Limited | Gatwick | 2016 |
| Basalt Global Limited | Christchurch | 2011 |
| Basalt Power Limited | Christchurch | 2019 |
| Bascott Renewables Limited | Poole | 2016 |
| Base Park Solar Limited | London | 2011 |
| Base Utilities & Civils Ltd | Waltham Abbey | 2023 |
| Baseline Power Limited | Brighouse | 2016 |
| Basildon Power Limited | Warrington | 2014 |
| Basin Bridge Solar Limited | Hove | 2013 |
| Bask Solar & EV UK Ltd | Belfast | 2025 |
| Bassingfield REP Limited | Nottingham | 2021 |
| Batchelor Air Conditioning & Refrigeration Limited | Olney | 2001 |
| Bath & West Community Solar 2 Limited | London | 2010 |
| Bath & West Community Solar 3 Limited | London | 2022 |
| Bath and West Community Solar Limited | London | 2011 |
| Bath Capital Limited | Bristol | 2024 |
| Bathgate Energy Storage Limited | London | 2019 |
| Batleur Limited | Dunblane | 2018 |
| Batsworthy Cross Wind Farm Limited | Kings Langley | 2014 |
| Battens Farm Solar Park Limited | Exeter | 2012 |
| Battens South Solar Limited | London | 2024 |
| Battery Asset Management Limited | London | 2019 |
| Battery Box Limited | London | 2022 |
| Battery Energy Storage Solutions Limited | London | 2018 |
| Battery Storage Enterprises Limited | Braintree | 2022 |
| Battery Storage Projects Limited | Braintree | 2022 |
| Baudet Equestrian Limited | Huntingdon | 2012 |
| Bauer Grant Contracts Ltd | Sheffield | 2018 |
| Bavington Mount Energy Limited | Faversham | 2014 |
| Bay Farm Power Limited | Wellingborough | 2013 |
| Baynes Air Conditioning Ltd | Manchester | 2020 |
| Bayston (Yorkshire) Limited | Brough | 2015 |
| Baywa R.E. Energy Trading UK Limited | London | 2024 |
| Baywa R.E. UK (Developments) Limited | London | 2013 |
| Baywrasse Enterprises Ltd | Shetland | 2018 |
| Bazaarya Ltd | London | 2025 |
| BB Ice Limited | Letchworth Garden City | 2024 |
| BB2 Wind Farm Limited | London | 2019 |
| BBD Energy Ltd | London | 2024 |
| Bbee Ltd | Ruislip, | 2025 |
| Bbess Ltd | Castlewellan | 2023 |
| Bbgn Energy Ltd | Horsham | 2022 |
| BC Utility Solutions Ltd | Knaresborough | 2024 |
| BCR So-Lar Ltd | Brighton | 2022 |
| BCT Conversion Ltd | London | 2022 |
| BD Energy Ltd | Omagh | 2018 |
| BD GAS Permits Ltd | Nottingham | 2020 |
| BD Permits Ltd | Nottingham | 2020 |
| BDM Mechanical Services Limited | Eastleigh | 2010 |
| BDP H2 Green UK Ltd | Bristol | 2024 |
| BE 2020 Limited | Bristol | 2014 |
| BE Brighter Energy Limited | Manchester | 2019 |
| Beachampton Solar Limited | London | 2011 |
| Beachampton Solar Project Holdco Limited | Reading | 2026 |
| Beachampton Solar Project Limited | Reading | 2019 |
| Beacon Electricians Ltd | Ashford | 2015 |
| Beacon FEN Energy Park Limited | London | 2021 |
| Beacon Renewables Limited | Lifton | 2014 |
| Beacon Solar Limited | Cardiff | 2024 |
| Beacons Cross Solar Limited | London | 2013 |
| Beacons Rural Energy Ltd | Brecon | 2026 |
| Beam Renewables Ltd | London | 2026 |
| Beane Energy Limited | Kings Langley | 2023 |
| Bearley Farm Green Energy Limited | Melton Mowbray | 2017 |
| Bears Down Windfarm Limited | London | 1992 |
| Bears GAS Services Ltd | Suffolk | 2025 |
| Bearsden Bess Ltd | London | 2022 |
| Bearus Consulting Ltd | Kirriemuir | 2018 |
| Beason's Aircon & Refrigeration Ltd | Alcester | 2018 |