| Biometan (UK) 2 Ltd | Leeds | 2025 |
| Biometan (UK) 3 Ltd | Leeds | 2026 |
| Biometan (UK) 4 Ltd | Leeds | 2026 |
| Biometan (UK) 5 Ltd | Leeds | 2026 |
| Biomethane (Castle Eaton) Limited | Ely | 2015 |
| Bionex Energy Savings Ltd | Basildon | 2025 |
| Biopower (Hartlepool) Limited | Stokesley | 2016 |
| Biosouth Energy Limited | Stroud | 2024 |
| Biosouth Limited | Stroud | 2020 |
| Biosus Energy Ltd | Aberdeen | 2013 |
| Biotec Renewables Limited | Littleborough | 2023 |
| Bioticnrg Operations Limited | Wellingborough | 2006 |
| Birch Electrical Network Services Limited | Ipswich | 2010 |
| Birch Electrical Services London Limited | London | 2014 |
| Birch Energy Limited | South Humberside | 1999 |
| Birch Estate Solar Limited | London | 2014 |
| Birch Solar Farm CIC | London | 2015 |
| Birch Solar Park Limited | London | 2021 |
| Birchall Green Solar Farm Limited | London | 2021 |
| Birchwood Renewables Limited | Dorchester | 2015 |
| Birkenhead Battery Storage Limited | Cheltenham | 2021 |
| Birkenhead Project Company NO.1 Limited | Blackburn | 2026 |
| Birkenside Wind Turbine Ltd | Earlston | 2012 |
| Birkett Projects Ltd | Morpeth | 2025 |
| Birmingham Air Conditioning Ltd | Sutton Coldfield | 2022 |
| Birmingham BIO Power Limited | London | 2012 |
| Birmingham Cooling Ltd | Birmingham | 2020 |
| Birmingham District Energy Company Limited | London | 2006 |
| Birnie Gowkhill Energy Ltd | Peterhead | 2014 |
| Birsay Energy Limited | Grange Over Sands | 2000 |
| Birtley Battery Storage Limited | Bristol | 2024 |
| Bishop Aukland Energy Park Limited | London | 2021 |
| Bishop Stortford Energy Park Limited | London | 2021 |
| Bishops DAL Energy Storage Limited | Kings Langley | 2024 |
| Bishopstone Solar Limited | London | 2021 |
| Bishopthorpe Wind Farm Limited | London | 2011 |
| Bison Electrical & Management Ltd | Bradford | 2026 |
| Bitterley Biogas AD Limited | Ludlow | 2016 |
| BJB Renewables Ltd | Sutton Coldfield | 2013 |
| BJD Renewables Ltd | Newtown | 2022 |
| BJT Electrical Services Limited | Hertford | 2015 |
| BK Energy Ltd. | Magherafelt | 2015 |
| BK Pegasus GAS, Electrical and Plumbing Ltd | Birmingham | 2025 |
| BL Solar 11 (Mundham) Limited | Chichester | 2024 |
| BL Solar 12 (Helios Energy Park) Limited | Chichester | 2024 |
| BL Solar 2 Limited | London | 2013 |
| BL Solar Energy Ltd | Sevenoaks | 2025 |
| BL Wind Limited | Kings Langley | 2013 |
| Blable Ltd | Wadebridge | 2013 |
| Blaby Solar Farm Limited | London | 2015 |
| Black Brook CHP Ltd | London | 2021 |
| Black Country Utilities Limited | Stourbridge | 2010 |
| Black Dog Biogas Limited | Stafford | 2013 |
| Black Dubb Wind Farm Limited | London | 2024 |
| Black Hill Wind Farm Holdco Limited | London | 2012 |
| Black Hill Wind Farm Limited | London | 2002 |
| Black Hill Wind Farm Topco Limited | London | 2012 |
| Black Ice CPD Limited | Manchester | 2016 |
| Black Knowe Energy Limited | Motherwell | 2022 |
| Black Knowe WF Limited | Motherwell | 2022 |
| Black Mountain Investments Ltd | Bourne | 2025 |
| Black Qube Property Services Ltd | London | 2023 |
| Black Shed Generation Limited | Greenock | 2017 |
| Black Swan Energy Ltd | London | 2023 |
| Black Torrington Solar Ltd | London | 2021 |
| Blackaton Power Limited | Taunton | 2013 |
| Blackawall Developments Ltd | Glasgow | 2013 |
| Blackbridge TGS 1 Limited | Bedford | 2014 |
| Blackburn Landholdings Limited | Bude | 2025 |
| Blackcraig Wind Farm (Scotland) Limited | Edinburgh | 2014 |
| Blackdown Solar Power Limited | Reading | 2010 |
| Blackdyke Bess Limited | London | 2022 |
| Blackford Renewables Ltd | Aberdeen | 2022 |
| Blackhill 2023 Limited | Exeter | 2023 |
| Blackhill Wind Ltd | Newry | 2013 |
| Blackhillock Flexpower Ltd | Glasgow | 2021 |
| Blackhouse Wind Farm Limited | Glasgow | 2012 |
| Blacklock Group Limited | Bangor | 2023 |
| Blackmead Hub West Limited | London | 2015 |
| Blackpark Energy Storage Limited | Edinburgh | 2018 |
| Blackpool East Solar Farm Limited | Arundel | 2020 |
| Blackpool Turbine Ltd | Wadebridge | 2013 |
| Blackstone Edge Wind Farm Limited | London | 2010 |
| Blackswanobsidian.Trade Ltd | Braintree | 2025 |
| Blackthorn Energy Limited | Weybridge | 2020 |
| Blackwater Electricity Limited | Larne | 2000 |
| Blackwell Grange Solar Farm Limited | Reading | 2013 |
| Blackwood Wind Farm Limited | Edinburgh | 2023 |
| Blaenau Gwent Solar Limited | London | 2017 |
| Blaencilgoed Enterprises Limited | Narberth | 2013 |
| Blaencothi Energy Park Limited | Cardiff | 2021 |
| Blaenpant Wind Turbine Limited | London | 2016 |
| Blaguegate Power Limited | Salford Quays | 2023 |
| Blair Electrical Services Limited | Wellingborough | 2003 |
| Blairhill Water Power Limited | Kinross | 1991 |
| Blairmore Hydro Ltd | Dunoon | 2012 |
| Blairside Limited | Girvan | 2023 |
| Blaise Biogas Limited | Ely | 2018 |
| Blaise Developments Limited | Stokesley | 2018 |
| Blakeways Access Limited | Cradley Heath | 2017 |