| Crystal RIG III Limited | Glasgow | 2009 |
| Crystal RIG IV Limited | Glasgow | 1996 |
| Crystal RIG Windfarm Limited | London | 2002 |
| Crystalair Limited | Peterborough | 1991 |
| CS Engineering & Pipework Services Ltd | Bristol | 2009 |
| CS Hvac Limited | Loughton | 2008 |
| CS UK Holdings III Limited | London | 2017 |
| CS16 Limited | London | 2016 |
| CS17 Limited | London | 2016 |
| CS18 Limited | London | 2016 |
| CSC Greenenergy Ltd | Bridgend | 2024 |
| CSE Air Conditioning Limited | Warwick | 2022 |
| CSE22 Limited | London | 2017 |
| CSE23 Limited | London | 2017 |
| CSE25 Limited | London | 2018 |
| CSE26 Limited | Stockport | 2018 |
| CSE27 Limited | London | 2018 |
| CSE28 Limited | London | 2018 |
| CSE29 Limited | London | 2018 |
| CSE30 Limited | London | 2018 |
| CSE31 Limited | London | 2018 |
| CSE32 Limited | London | 2018 |
| CSE33 Limited | London | 2018 |
| CSE34 Limited | London | 2018 |
| CSE37 Limited | London | 2022 |
| CSE38 Limited | London | 2022 |
| CSE39 Limited | London | 2022 |
| CSE41 Limited | London | 2022 |
| CSE42 Limited | London | 2022 |
| CSE43 Limited | London | 2022 |
| CSE44 Limited | London | 2022 |
| CSE45 Limited | London | 2022 |
| CSE46 Limited | London | 2022 |
| CSE48 Limited | London | 2022 |
| CSE50 Limited | London | 2022 |
| CSE51 Limited | London | 2022 |
| CSE52 Limited | London | 2022 |
| CSE53 Limited | London | 2022 |
| CSE54 Limited | London | 2022 |
| CSE55 Limited | London | 2022 |
| Csgh Solar (1) Ltd | London | 2017 |
| Csgh Solar Ltd | London | 2017 |
| CSI Biosphera Sapi International Limited | Witham | 2023 |
| CSI Biosphera Sapi Limited | Witham | 2023 |
| CSL (Air Conditioning) Limited | London | 2008 |
| CSO Heating Limited | Norwich | 2015 |
| Csonea Limited | London | 2017 |
| Csoneb Limited | London | 2017 |
| Csonec Limited | London | 2017 |
| Csptuk 1 Ltd | London | 2017 |
| Csptuk 2 Ltd | London | 2017 |
| CSS Electrical Ltd. | Darlington | 2012 |
| CSS Solar Ltd | Weston-Super-Mare | 2022 |
| CST Electrical & Cooling Limited | Bridgend | 2017 |
| Ctech Air Conditioning Ltd | Bristol | 2022 |
| CTH Electrical Services Ltd | Hornchurch | 2019 |
| Cubico Sun II Limited | London | 2023 |
| Cubico Sun Limited | London | 2022 |
| Cubico Sustainable Investments Holdings Limited | London | 2014 |
| Cubico Sustainable Investments Limited | London | 2014 |
| Cubico UK Development (Wind 1) Limited | London | 2024 |
| Cubico UK Development Limited | London | 2021 |
| CUC Properties HMO Management Limited | Bradford | 2023 |
| Cuckoo Hill Solar Farm Limited | London | 2025 |
| Cuckoo Solar Limited | London | 2012 |
| Cucumber Climate Control Ltd | Radlett | 2018 |
| Cucumber Eco Renewables Ltd | Manchester | 2025 |
| Cuil Burn Hydropower Ltd | Cardiff | 2019 |
| Culbirnie Parks Renewable [2016] Ltd | Turriff | 2016 |
| Culham Storage Limited | London | 2022 |
| Cullion Wind Farm II Limited | Lisburn | 2023 |
| Cullion Wind Farm Limited | Lisburn | 2020 |
| Cullyrammer Wind Ltd | Belfast | 2017 |
| Culmore Energy Ltd | Limavady | 2015 |
| Culsalmond Air Limited | Aberdeen | 2014 |
| Culvery Power Limited | Bristol | 2014 |
| Culvie Hill Wind Limited | Turriff | 2015 |
| Culvie Wind (Holdings) Ltd | Aberdeen | 2018 |
| Culvie Wind Limited | Aberdeen | 2015 |
| Culworth Grounds Solar Limited | Cheltenham | 2013 |
| Culzean Generation Limited | Warrington | 2017 |
| Culzean Power Limited | Warrington | 2014 |
| Culzean W2E Limited | Warrington | 2018 |
| Cumberhead West Wind Farm Ltd. | Glasgow | 2016 |
| Cumberhead Wind Energy Limited | London | 2014 |
| Cumbria Biogas Limited | London | 2016 |
| Cumbria Energy Limited | Market Hill | 2024 |
| Cumbria Wind Limited | London | 2013 |
| Cumby's Farm Solar Park Limited | Houghton-Le-Spring | 2022 |
| Cummins ESB Nigeria Limited | London | 2009 |
| Cumnor Solar Farm Limited | London | 2021 |
| Cupar Energy Storage Park Limited | London | 2023 |
| Curlew Power Limited | London | 2014 |
| Curragh Road Wind Limited | Belfast | 2016 |
| Curran Energy Supply Limited | Chorley | 2025 |
| Current Energies Ltd | Axminster | 2025 |
| Current Energy Ltd | Axminster | 2025 |
| Current Sparx Electrical Ltd | London | 2021 |
| Curryfree Wind Farm Limited | Londonderry | 2008 |
| Curtain Road Developments 27 Limited | Norwich | 2021 |