| Capital Stage Manor Farm Ltd. | London | 2014 |
| Capitol Essential Services Limited | Cheam | 2008 |
| Caplich Wind Farm Ltd | Motherwell | 2011 |
| Caplor Energy Limited | Birmingham | 2001 |
| Capri Energy Limited | London | 2014 |
| Capricorn Partners Limited | Pinner | 2014 |
| Caps Clean Energy Limited | Ilford | 2024 |
| Captain ZOG Ltd | St Abbs | 2012 |
| Captured Carbon (N.I.) Limited | Belfast | 2017 |
| Car Charging Limited | Braintree | 2020 |
| Car Duibh Wind Farm Limited | London | 2020 |
| Cara Renewables Limited | London | 2015 |
| Caranday Electrics Limited | Norwich | 2011 |
| Carbon Capture Reuse Limited | London | 2019 |
| Carbon Catch Limited | Cardiff | 2013 |
| Carbon Cooling Ltd | Coventry | 2011 |
| Carbon Credit Group Ltd | Chorley | 2025 |
| Carbon Free Neilston Ltd | Kings Langley | 2009 |
| Carbon Point Connections Ltd | Leicester | 2021 |
| Carbon Reduction Committed Ltd | Sale | 2010 |
| Carbon Saving Generation Limited | Norwich | 2011 |
| Carbon Strategic Management Group Limited | Weymouth | 2022 |
| Carbon Zero Markets Limited | King'S Lynn | 2020 |
| Carcant Windfarm (Scotland) Limited | Edinburgh | 2007 |
| Cardan Air Conditioning Limited | West Yorkshire | 2002 |
| Cardenden Heat and Power Ltd | Cardenden | 2011 |
| Cardiff Air Conditioning Ltd | Bristol | 2025 |
| Cardiff Cooling Limited | Cardiff | 2024 |
| Cardiff SD Limited | London | 2015 |
| Cardiff Wind Park Limited | Stroud | 2007 |
| Cardinal Bear Ltd | London | 2026 |
| Care Power (Barnsley) Limited | London | 2016 |
| Care Power (Berkeley) Limited | London | 2017 |
| Care Power (Brentwood) Limited | London | 2018 |
| Care Power (Brook Farm) Limited | London | 2017 |
| Care Power (Burwell 1) Limited | London | 2017 |
| Care Power (Drumcross) Limited | Glasgow | 2020 |
| Care Power (Newtonwood) Limited | London | 2018 |
| Care Power (North Tawton) Limited | London | 2019 |
| Care Power (Upton) Limited | London | 2019 |
| Care Power (Wolverhampton) Limited | London | 2019 |
| Cargen Power Limited | Edinburgh | 2011 |
| Cargo Battery Storage Limited | Stonehouse | 2022 |
| Cariad Wind Consulting Ltd. | Llandudno Junction | 2022 |
| Caricool Limited | Cardiff | 2020 |
| Caring in Care Limited | Dereham | 2009 |
| Carlam Hill Education C.I.C. | London | 2015 |
| Carlin Utilities Limited | Nr. Leyland | 2021 |
| Carlisle Estate Solar Limited | London | 2014 |
| Carloggas Solar Park Limited | Bristol | 2013 |
| Carlogic Limited | Warrington | 1993 |
| Carlton Energy NO: 1 Limited | Middlesbrough | 2024 |
| Carlton Energy NO: 2 Limited | Middlesbrough | 2024 |
| Carlton Energy NO: 3 Limited | Middlesbrough | 2024 |
| Carlton Energy NO: 4 Limited | Middlesbrough | 2024 |
| Carlton Energy NO: 5 Limited | Middlesbrough | 2024 |
| Carlton Power Developments NO. 2 Limited | Stokesley | 2021 |
| Carlton Power Developments NO. 4 Limited | Stokesley | 2021 |
| Carlton Power Developments NO. 6 Limited | Stokesley | 2021 |
| Carlton Power Developments NO: 17 Limited | Middlesbrough | 2024 |
| Carlton Solar Farm Limited | Rugby | 2020 |
| Carlton Wood Renewables Limited | Newark | 2012 |
| Carmarthen Bess Limited | Cardiff | 2023 |
| Carmoney Energy Limited | Belfast | 2013 |
| Carn Fearna Wind Farm Limited | London | 2022 |
| Carn Hill Windfarm Limited | Belfast | 2010 |
| Carn Nicholas Solar Limited | Cheltenham | 2020 |
| Carnalbanagh Wind Farm Ltd | Lisburn | 2016 |
| Carnbuck Energy Limited | Larne | 2022 |
| Carnegie (BES) Ltd | London | 2020 |
| Carnemough Solar Project Limited | Hove | 2014 |
| Caroline Louise Farms Limited | London | 2008 |
| Caron Renewables Ltd | Carmarthen | 2015 |
| Carr Farm Biogas Limited | Blackpool | 2010 |
| Carr Farm Solar Limited | Arundel | 2022 |
| Carr House Farm Energy Centre Limited | Norwich | 2022 |
| Carraig Gheal Wind Farm Limited | London | 2011 |
| Carravindoon Limited | Wimborne | 2020 |
| Carrex Flexible Storage Limited | London | 2018 |
| Carrick Road Energy IRL Ltd | Banbridge | 2017 |
| Carrick Road Holdings Limited | Banbridge | 2016 |
| Carricklee Breeze Ltd | Strabane | 2012 |
| Carrier Import & Export Co., Ltd | West Midlands, England | 2024 |
| Carrigmona Solar Limited | Armagh | 2026 |
| Carrington Community Solar Energy Limited | Frodsham | 2021 |
| Carrington Generation Limited | Kirkby Lonsdale | 2018 |
| Carrington Power Limited | Manchester | 2003 |
| Carrington Storage Limited | London | 2008 |
| Carrino Eco Ltd | Holmfirth | 2009 |
| Carrog Storage Facility Limited | Arundel | 2022 |
| Carron Energy Limited | Cardiff | 2009 |
| Carrow Solar Limited | London | 2011 |
| Carrowdore Solar Limited | Belfast | 2014 |
| Carrstone Renewables Ltd | Guildford | 2025 |
| Carscreugh Renewable Energy Park Limited | Kings Langley | 2006 |
| Carse Gray Renewables Limited | Stratford-Upon-Avon | 2013 |
| Carsebank Solar Limited | Edinburgh | 2015 |
| Carsena Energy Holdco Ltd | Belfast | 2024 |
| Carsington Wind Energy Limited | London | 2004 |
| Cart Right Limited | Morecambe | 2006 |