| Brampton Power Limited | Tamworth | 2024 |
| Branatiff Limited | Nottingham | 2015 |
| Branden Solar Parks (Holdings) Limited | London | 2012 |
| Branden Solar Parks Limited | London | 2012 |
| Brandon Road Solar Limited | Liverpool | 2022 |
| Brankston Bess Ltd | London | 2023 |
| Branna Renewables (Larkhall) Ltd | Motherwell | 2009 |
| Brannigan Energy Limited | Dungannon | 2016 |
| Bransholme Solar C.I.C. | London | 2015 |
| Branston Solar Park Limited | London | 2013 |
| Braston New Energy Limited | Lydney | 2023 |
| Bratton Fleming Limited | London | 2011 |
| Braydon Manor Community Solar C.I.C. | Scorrier, Redruth | 2014 |
| Braydon Manor Renewable Energy Limited | Bath | 2014 |
| BRC Electrical Ltd | Aberdeen | 2015 |
| BRD Builders Limited | Buckingham | 2014 |
| BRD Wind Limited | Belfast | 2013 |
| Breach Farm Energy Storage Limited | London | 2018 |
| Bread and Shutter Limited | Sutton | 2007 |
| Breagho Limited | Belfast | 2013 |
| Breathe Pure Limited | Greenham | 2024 |
| Breck Solar Limited | London | 2013 |
| Brecon Power Ltd | Warrington | 2014 |
| Breda Wind Energy Limited | Edinburgh | 2023 |
| Breed Energy Limited | London | 2018 |
| Breen Air Ltd | Strabane | 2017 |
| Breeze Air Conditioning Ltd | Nottingham | 2021 |
| Breeze Power Ltd | Doncaster | 2012 |
| Breezeright Ltd | Caterham | 2026 |
| Breezi Cooling UK Ltd | Banbury | 2025 |
| Breezy Hill Energy Limited | Edinburgh | 2022 |
| Breezy Hill Wind Ltd | Craigavon | 2012 |
| Breighton Storage Facility Limited | Arundel | 2024 |
| Brendan Duggan Ltd | Manchester | 2011 |
| Brenig Wind Limited | London | 2006 |
| Brent I Limited | Aylesbury | 2025 |
| Brentwood Electrical Ltd | Ongar | 2018 |
| Brett Valley Energy Reserve Ltd | London | 2025 |
| Bretton Hall Solar Farm Ltd | Caernarfon | 2025 |
| Breva Powervale Limited | Morpeth | 2020 |
| Brewgas Suppliers Ltd | Swansea | 2025 |
| BRI Wind Farms 4 Limited | Belfast | 2016 |
| BRI Wind Farms 6 Limited | Belfast | 2018 |
| Brickkiln Farm Solar Limited | London | 2011 |
| Brickledons Farm Bess Limited | London | 2025 |
| Bridge Energy (NI) Limited | Banbridge | 2014 |
| Bridge Farm Renewable Energy Limited | Reading | 2023 |
| Bridge of Weir Hydro Ltd | West Kilbride | 2026 |
| Bridge Road Farm Limited | Ballymena | 2012 |
| Bridgegate Utilities Ltd | London | 2025 |
| Bridgen Investments Limited | London | 2006 |
| Bridgend Energy Limited | Stormy Down | 2026 |
| Bridgend Power Limited | Wolverhampton | 2022 |
| Bridgewater Solar Limited | London | 2010 |
| Bridgwater Green Limited | London | 2020 |
| Brigg Lane Biogas Limited | Ely | 2016 |
| Briggs Climate Control Ltd | Bristol | 2019 |
| Brigh Wind Ltd | Cookstown | 2012 |
| Brighouse Power Limited | London | 2025 |
| Bright Base Ltd | Bishopton | 2025 |
| Bright Electrical Ltd | Southampton | 2014 |
| Bright Energy Supply NI Limited | Newtownabbey | 2018 |
| Bright Renewable Energy Ltd | Liverpool | 2024 |
| Bright Sky Solar Limited | Poole | 2012 |
| Bright Sparks & SON Limited | Windsor | 2013 |
| Bright Star Energy Ltd | Dagenham | 2017 |
| Bright Star Energy Solutions Ltd | Dundee | 2024 |
| Bright Star Utilities Ltd | Dundee | 2019 |
| Brightline Ever Ltd | Scunthorpe | 2025 |
| Brighton GAS Safety.Com Limited | Hove | 2011 |
| Brightoned Energy Ltd | London | 2026 |
| Brightside Connect Utilities Limited | Stanford-Le-Hope | 2018 |
| Brightside Connections 01 Limited | London | 2023 |
| Brightside Connections 02 Limited | London | 2023 |
| Brightside Connections Limited | London | 2023 |
| Brightside Holdings Limited | Brighton | 2018 |
| Brightside Newco Limited | London | 2024 |
| Brightway Hub Limited | Bishop'S Stortford | 2024 |
| Brilliant Energy Services Ltd. | London | 2003 |
| Brimble Tech Ltd | Marlow | 2019 |
| Brindle Electrical Services Limited | Middlesbrough | 2008 |
| Brinklow Bioenergy Ltd | Tamworth | 2025 |
| Brishey Wind Farm Limited | Lisburn | 2020 |
| Bristol Agricultural Waste Plant Holdings Limited | London | 2026 |
| Bristol Agricultural Waste Plant Limited | London | 2026 |
| Bristol Biofuel Plant Limited | London | 2026 |
| Bristol Heat Networks Limited | London | 2018 |
| Bristol Living Limited | Bristol | 2007 |
| Bristol LR (Hersey Gardens) Limited | Leeds | 2025 |
| Bristol LR (Severn Road) Limited | Leeds | 2025 |
| Bristol LR (Smoke Lane) Limited | Leeds | 2025 |
| Bristol Port Wind Park Limited | Stroud | 2005 |
| Bristol SD Limited | London | 2015 |
| Britannia Air Conditioning Ltd | Sutton Coldfield | 2019 |
| Britannia Electrical Solutions Ltd | Sandbach | 2012 |
| Britannia Energy Limited | London | 2015 |
| Brite Electrical Ltd | Manchester | 2021 |
| Britford Solar Connection Limited | London | 2015 |
| British GAS Limited | Windsor | 2013 |
| British GAS Trading Limited | Berkshire | 1995 |