| Cairnknowe Windfarm Limited | Dumfries | 2019 |
| Cairnmore Hill Energy Limited | London | 2024 |
| Cairns Energy Ltd | Strathlachlan | 2023 |
| Cairntawie Wind Energy Limited | Edinburgh | 2025 |
| Cairnton Estate Renewables Limited | Shepton Mallet | 2025 |
| CAK Electrical Limited | Ilkeston | 2016 |
| Cal-Ty Stoves Ltd | Sudbury | 2019 |
| Calby Air Limited | London | 2003 |
| Calcot Electrical Services Ltd | Sandhurst | 2017 |
| Calder Water Community Wind Co Ltd | Edinburgh | 2011 |
| Caldicot Farmers' Solar Scheme Limited | London | 2014 |
| Cale Power Limited | Cardiff | 2008 |
| Caledon Green Generation Limited | Greenock | 2018 |
| Caledonia Offshore Wind Farm Limited | London | 2022 |
| Calibre Generation Limited | Bath | 2017 |
| California Energy Limited | Epsom | 2019 |
| Call OUT Services Ltd | Birmingham | 2023 |
| Callagheen Ltd | Omagh | 2017 |
| Callan Renewables Ltd | Armagh | 2014 |
| Callander Community Hydro Limited | Callander | 2011 |
| Callie's Solar Farm Limited | London | 2020 |
| Callington Solar Park Limited | Exeter | 2012 |
| Callisia Limited | Sunbury-On-Thames | 1965 |
| Callisterhall Limited | Edinburgh | 2021 |
| Cally Energy CIC | London | 2020 |
| Calm Charging Group Limited | Kings Langley | 2023 |
| Calm Charging Limited | Kings Langley | 2023 |
| Caloenergia UK Ltd | Altrincham | 2022 |
| Calow Solar Limited | London | 2014 |
| Calton Renewables Limited | Cumnock | 2012 |
| Calzach Limited | Belfast | 2012 |
| CAM Burn Wind Farm Limited | Lisburn | 2021 |
| CAM Electrical Limited | Carshalton | 2018 |
| Camber Solar Project Limited | Exeter | 2015 |
| Camblesforth Solar Farm Limited | Rugby | 2019 |
| Camborne Energy Storage Limited | London | 2015 |
| Cambria Hydrogen Ltd | Taunton | 2020 |
| Cambrian Refrigeration Limited | Swansea | 2010 |
| Cambrian Renewable Energy Limited | London | 2003 |
| Cambrian Wind Energy Limited | London | 1997 |
| Cambridge Aircon Limited | Cambridge | 2024 |
| Cambridge Biopower Limited | Peterborough | 2018 |
| Cambridge Biorenewables Ltd | Bishop Auckland | 2012 |
| Cambridge Cooling Services Ltd | Newmarket | 2015 |
| Cambridge Renewable Solutions Ltd | Cardiff | 2025 |
| Cambridge Solar Power Limited | London | 2014 |
| Camburn Developments Ltd | Coleraine | 2021 |
| Cameron Turbine Ltd | Magherafelt | 2015 |
| Camieston Renewables Limited | Melrose | 2016 |
| Camilty Windfarm Limited | London | 2011 |
| Camlough Wind Limited | Belfast | 2012 |
| Cammas Hall Partnership Limited | Bishop'S Stortford | 2012 |
| Cammell Laird (North-East) Limited | Leeds | 1977 |
| Cammell Laird (Teesside) Limited | 33 Wellington Street | 1987 |
| Cammell Laird (Tyneside) Limited | 33 Wellington Street | 1994 |
| Cammell Laird (Wearside) Limited | Leeds | 1995 |
| Camp Farm Green Energy Limited | London | 2022 |
| Camp Farm Solar Limited | London | 2024 |
| Campbell and Law Building Services Ltd | Upminster | 2018 |
| Campbell's Air Conditioning and Refrigeration Limited | Dumbarton | 2001 |
| Campbells Solar Farm Ltd | Edinburgh | 2023 |
| Campionwind Limited | Edinburgh | 2022 |
| Campus Link Limited | Radstock | 2010 |
| Camregan Renewables Limited | Girvan | 2011 |
| Camserney Hydro Scheme Limited | Perth | 2001 |
| Canada Farm Solar Park Limited | Gatwick | 2012 |
| Canada International Limited | London | 2006 |
| Canadian Solar Construction Limited | London | 2015 |
| Canadian Solar Israel Limited | London | 2017 |
| Canaird River Company Limited | Nr Ullapool | 2013 |
| Canba Powervale Limited | Morpeth | 2020 |
| Cancave Ltd | London | 2023 |
| Candwr Solar Farm Ltd | London | 2022 |
| Canigou Capital Ltd | London | 2014 |
| Canna Renewable Energy and Electrification Limited | Isle Of Canna | 2017 |
| Cannock Building Services Limited | Warrington | 2012 |
| Cannock Renewables Limited | Birmingham | 2014 |
| Canopus Farm Solar Limited | Hove | 2013 |
| Cantelupe Solar Limited | Reading | 2010 |
| Cantium Energy Limited | Norwich | 2008 |
| Cantlayhills Energy Limited | Edinburgh | 2017 |
| Cantor Energy Limited | London | 2017 |
| Capbal (Braco) Limited | London | 2022 |
| Capbal (Forfar) Limited | London | 2022 |
| Cape Horn Energy Limited | London | 2025 |
| Cape RE 2 Limited | Nottingham | 2015 |
| Cape RE 3 Limited | Nottingham | 2018 |
| Cape RE 4 Limited | Nottingham | 2019 |
| Cape RE Limited | Nottingham | 2014 |
| Capel Grange Solar Energy Limited | London | 2013 |
| Capelands Solar Farm Limited | Gatwick | 2014 |
| Capital Air CON Limited | Billericay | 2018 |
| Capital Air Conditioning (Wales) Limited | Cardiff | 2011 |
| Capital Electrical Solutions Ltd | Hornchurch | 2023 |
| Capital Energy Associates Limited | London | 2016 |
| Capital Energy Solutions Limited | Basildon | 2026 |
| Capital Stage Caddington II Limited | London | 2015 |
| Capital Stage Caddington Limited | London | 2014 |
| Capital Stage Cullompton Limited | London | 2013 |
| Capital Stage Hall Farm Limited | Edinburgh | 2013 |