| Capgemini Engineering | Paris, France | Visit site |
| Capgemini Invent | Paris, France | Visit site |
| Capital Energy | Pozuelo de Alarcón, Spain | Visit site |
| Capriole Construction Company L.L.C. | Dubai, United Arab Emirates | Visit site |
| Capstone Infrastructure Corporation | Toronto, Canada | Visit site |
| Capstone Power Solutions Ltd | Elland, United Kingdom | Visit site |
| Captain Green Solar | Sydney, Australia | Visit site |
| Captiva Asset Management | Oslo, Norway | Visit site |
| Captiva Asset Management | Göteborg, Sweden | Visit site |
| Captiva Asset Management | Bern, Switzerland | Visit site |
| Captivate Technology | Palmerston North, New Zealand | Visit site |
| Capwatt | Guarulhos, Brazil | Visit site |
| Carbon3 | Singapore, Singapore | Visit site |
| CarbonLeap | Amsterdam, Netherlands | Visit site |
| CarbonRun | Dartmouth, Canada | Visit site |
| Carbonade | Dimona, Israel | Visit site |
| Carcinus Ltd | Eastleigh, United Kingdom | Visit site |
| Cardinal Engineering Consultant Pvt. Ltd. | Ahmedabad, India | Visit site |
| Cardno | Brisbane, Australia | Visit site |
| Cares Renewables | Coimbatore, India | Visit site |
| Cargar | India | Visit site |
| Carku | Shenzhen Shi, China | Visit site |
| Carlo Maresca | Pescara, Italy | Visit site |
| Carnegie Clean Energy | Perth, Australia | Visit site |
| Carter Complete Building Services Ltd | Stoke-on-Trent, United Kingdom | Visit site |
| Casa dos Ventos Energias Renováveis | São Paulo, Brazil | Visit site |
| Casais Angola | Luanda, Angola | Visit site |
| Casais Construction | Mire de Tibães, Portugal | Visit site |
| Castle Surveys Ltd | Ashby-de-la-Zouch, United Kingdom | Visit site |
| Castle Surveys Ltd | Glasgow, United Kingdom | Visit site |
| Castle Surveys Ltd | London, United Kingdom | Visit site |
| Castle Surveys Ltd | Manchester, United Kingdom | Visit site |
| Castle Surveys Ltd | Edinburgh, United Kingdom | Visit site |
| Castrol | Reading, United Kingdom | Visit site |
| Catalyst | Dublin, Ireland | Visit site |
| Catapult Network | London, United Kingdom | Visit site |
| Catch Engineering | Calgary, Canada | · |
| Cbus Super Fund | Melbourne, Australia | Visit site |
| Cecil | Sydney, Australia | Visit site |
| Cefic | Brussels, Belgium | Visit site |
| Celestial Renewexperts LLP | Pune, India | Visit site |
| Celestica | Toronto, Canada | Visit site |
| CellCircle | Würzburg, Germany | Visit site |
| CellCube | Wiener Neudorf, Austria | Visit site |
| CellMine | Livingston, United Kingdom | Visit site |
| Cellfion | Stockholm, Sweden | · |
| Cellforce Power | Tübingen, Germany | Visit site |
| Celltech | Tampere, Finland | · |
| Cellula Robotics Ltd. | Burnaby, Canada | Visit site |
| Celynx AG | Zürich, Switzerland | Visit site |
| Cengiz Holding | Üsküdar, Türkiye | Visit site |
| Cenovus Energy | Calgary, Canada | Visit site |
| Centauri | Kingston, Canada | Visit site |
| Central Electricity Regulatory Commission (CERC) | New Delhi, India | Visit site |
| Central Maine Power Company | United States | Visit site |
| Central Steel Build | Kyneton, Australia | Visit site |
| Centre for Sustainable Energy | Bristol, United Kingdom | Visit site |
| Centro Energy | Changzhou Shi, China | Visit site |
| Centro Energy | China | Visit site |
| Centro Tecnológico EnergyLab | Vigo, Spain | Visit site |
| Centrum Wiskunde & Informatica | Amsterdam, Netherlands | Visit site |
| Centrum Wiskunde & Informatica | Coulsdon, United Kingdom | Visit site |
| Centum Electronics Ltd. | Bengaluru, India | Visit site |
| Centurion Battery | Roermond, Netherlands | · |
| Cenviro Group | Kuala Lumpur, Malaysia | Visit site |
| Ceramatec, Inc. | United States | Visit site |
| Ceres | Horsham, United Kingdom | · |
| Cero Generation | London, United Kingdom | Visit site |
| Cesbe Engenharia | Curitiba, Brazil | Visit site |
| Cetogenix | Rotorua, New Zealand | Visit site |
| Chandos Construction | Edmonton, Canada | Visit site |
| Changeworks | Edinburgh, United Kingdom | Visit site |
| Changhong Battery | Mianyang Shi, China | · |
| CharIN e.V. | Berlin, Germany | Visit site |
| CheckWatt | Danderyd, Sweden | · |
| Chemonics Egypt Consultants | Giza, Egypt | Visit site |
| Chengdu Sixpence Technology Co., Ltd. | China | Visit site |
| Chengdu Sixpence Technology Co., Ltd. | Chengdu Shi, China | Visit site |
| Cheshire Solar Solutions | Macclesfield, United Kingdom | · |
| Chiko Solar | Shanghai, China | Visit site |
| China BAK Battery Co., Ltd. | Shenzhen Shi, China | Visit site |
| China Best Solar power products | Guangzhou Shi, China | · |
| China Datang Corp Renewable Power Co Ltd | Beijing, China | Visit site |
| China Energy Engineering Group Co. Ltd. | Beijing, China | Visit site |
| China sunergy (nanjing) co.,ltd | China | · |
| China-Manufacturer | China | Visit site |
| Chinaland Solar Energy Co., Ltd | China | Visit site |
| Chint Cable | Bathinda, India | Visit site |
| Chint Power Latam | São Paulo, Brazil | · |
| Chint Solar Europe | Hamburg, Germany | · |
| Chiron Energy | Rozzano, Italy | Visit site |
| Chisage ESS | China | Visit site |
| Ciel & Terre India | Bengaluru, India | Visit site |
| Ciel & Terre International | Sainghin-en-Mélantois, France | Visit site |
| Ciel & Terre Taiwan | 臺南市, Taiwan | Visit site |
| Ciera Group | Calgary, Canada | Visit site |
| Circadian Technologies | Berlin, Germany | Visit site |
| Circal | Blackrock, Ireland | Visit site |
| Circmet AS | Oslo, Norway | · |
| Circu Li-ion | Ludwigshafen am Rhein, Germany | Visit site |
| Circulair Friesland | Leeuwarden, Netherlands | Visit site |
| Circular Renewables Ltd | Goole, United Kingdom | Visit site |
| Circular Silicon | Braunschweig, Germany | · |
| Circunomics | Mainz, Germany | Visit site |
| Circutor | Sabadell, Spain | Visit site |
| Cirtem | Sainte-Foy-d'Aigrefeuille, France | Visit site |
| Citicore Renewable Energy Corporation (CREC) | San Juan, Philippines | Visit site |
| Citus Power | Sarıyer, Türkiye | Visit site |
| City Solar | Dubai, United Arab Emirates | · |
| City of Amsterdam | Dunabogdány, Hungary | Visit site |
| City of Edmonton | Edmonton, Canada | Visit site |
| City of Toronto | Toronto, Canada | Visit site |
| City to Surf Solar | Geelong, Australia | Visit site |
| Ciudadenergía | Madrid, Spain | Visit site |
| Clamore Solar Eswatini | Mbabane, Eswatini | Visit site |
| Clarke Energy | Liverpool, United Kingdom | Visit site |
| Clean Canarian Energy | Telde, Spain | Visit site |
| Clean Energy Association of British Columbia (CEBC) | Vancouver, Canada | Visit site |
| Clean Energy Canada | Vancouver, Canada | · |
| Clean Energy Council | Melbourne, Australia | Visit site |
| Clean Energy Pipeline | London, United Kingdom | Visit site |
| Clean Growth Fund | London, United Kingdom | · |
| Clean Horizon | Paris, France | · |
| Clean Kinetics Pte Ltd | Singapore, Singapore | · |
| Clean NRG Solar | Specialists for Solar Panel & Battery Storage In Perth | Perth, Australia | Visit site |
| Clean Power Hydrogen (CPH2) | Kendal, United Kingdom | · |
| CleanEarth | Wadebridge, United Kingdom | Visit site |
| CleanHedge Verde | Mumbai, India | Visit site |
| CleanIQ | Komotini, Greece | Visit site |
| CleanInnoGen Energy Solutions | Kanata, Canada | Visit site |
| CleanMax | Mumbai, India | Visit site |
| CleanTech Services Pte Ltd | Singapore, Singapore | Visit site |
| Cleanearth | Lashibi, Ghana | Visit site |
| Cleanergy Maroc | Casablanca, Morocco | · |
| Cleantech Commons™ | Peterborough, Canada | Visit site |
| Cleanwatts | Coimbra, Portugal | Visit site |
| ClearBlue Markets | Toronto, Canada | Visit site |
| ClearVue Technologies Limited (ASX:CPV) | Australia | Visit site |
| Clearlight Energy | Oakville, Canada | Visit site |
| Clearpath Robotics by Rockwell Automation | Waterloo, Canada | Visit site |
| Clemens Kraft AS | Oslo, Norway | Visit site |
| Clemessy | Mulhouse, France | Visit site |
| Clever Solar Devices | Torralba de Calatrava, Spain | Visit site |
| CleverNett | Kortrijk, Belgium | Visit site |
| ClimEtSan-OnTheGround | Bonn, Germany | Visit site |
| Clima Rio Solar | Vitória, Brazil | Visit site |
| Climacool by Blue Pearl Energy | La Boisse, France | Visit site |
| Climagea | Pomezia, Italy | Visit site |
| Climate Council | Australia | Visit site |
| Climate Council | Melbourne, Australia | Visit site |