| CMS Albiñana & Suárez de Lezo | Barcelona, Spain | Visit site |
| CMS SURVEYORS | Sydney, Australia | Visit site |
| CNR (Compagnie Nationale du Rhône) | Lyon, France | Visit site |
| CNR Construction | Pleumeleuc, France | Visit site |
| CNTE | China | Visit site |
| COGECLIM | France | Visit site |
| COMBATT S.A. | Athina, Greece | Visit site |
| CONGEOCON | São Paulo, Brazil | Visit site |
| CONSEJO DE PROFESIONALES EN ENERGÍA FOTOVOLTAICA - CPEF | San José del Castillo, Mexico | Visit site |
| CONSGA BIC SAS | Bogotá, Colombia | Visit site |
| CONSTRUCCIONES RUBAU | Barcelona, Spain | Visit site |
| CONVERDAN A/S | Vojens, Denmark | Visit site |
| CORE Geomatics | Calgary, Canada | Visit site |
| CPB Contractors | Sydney, Australia | Visit site |
| CPD Powerline Ltd | Armagh, United Kingdom | Visit site |
| CPM Engenharia - 35 anos | Passos, Brazil | Visit site |
| CR2P Photovoltaïque | Saint-Paul-lès-Dax, France | Visit site |
| CRE - Commission de régulation de l'énergie | Paris, France | Visit site |
| CREC - Clúster de Residus de Catalunya | Barcelona, Spain | Visit site |
| CRU | London, United Kingdom | Visit site |
| CS Instruments Turkey | Pendik, Germany | Visit site |
| CST Energy | Chiva, Spain | Visit site |
| CTCI | 臺北市, Taiwan | Visit site |
| CTECHi | Burk's Falls, Canada | Visit site |
| CW ENERJİ | Döşemealtı, Türkiye | Visit site |
| CWHI (CNOOD-Wenchong Heavy Industries) | Guangzhou Shi, China | Visit site |
| CWP Energy | United Kingdom | Visit site |
| CWP Global | Singapore | Visit site |
| CYSORE | León, Mexico | Visit site |
| Cables RCT | Zaragoza, Spain | Visit site |
| Cableworld | Bolton, United Kingdom | Visit site |
| Cabur | Altare, Italy | Visit site |
| Cadre AS | Kristiansand, Norway | Visit site |
| Cairn Risk | Glasgow, United Kingdom | Visit site |
| Calderys | Paris, France | Visit site |
| Calik Holding | Şişli, Türkiye | Visit site |
| Caltech Group | Calgary, Canada | Visit site |
| Cambridge GaN Devices Ltd | Cambridge, Taiwan | Visit site |
| Camco | London, United Kingdom | Visit site |
| Camille Bauer Metrawatt AG | Wohlen, Switzerland | Visit site |
| Canadian Climate Institute / Institut climatique du Canada | Bobcaygeon, Canada | Visit site |
| Canadian Hydrogen Association (CHA) | Vancouver, Canada | Visit site |
| Canadian Steel Producers Association (CSPA) | Ottawa, Canada | Visit site |
| Canbat | Vancouver, Canada | Visit site |
| Cando Solar | China | Visit site |
| Canoe | Stavanger, Norway | Visit site |
| Canopy Cameroun SARL | Paris, Cameroon | Visit site |
| Canopy Power | Melbourne, Australia | Visit site |
| Capcora | Frankfurt am Main, Germany | Visit site |
| Capgemini Invent | Paris, France | Visit site |
| Capriole Construction Company L.L.C. | Dubai, United Arab Emirates | Visit site |
| Captiva Asset Management | Bern, Norway | Visit site |
| Captivate Technology | Palmerston North, New Zealand | Visit site |
| Capwatt | Guarulhos, Brazil | Visit site |
| Carbon3 | Singapore | 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 |
| 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 |
| 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 |
| Castrol | Reading, United Kingdom | Visit site |
| Catalyst | Dublin, Ireland | Visit site |
| Catapult Network | London, United Kingdom | Visit site |
| 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 |
| Cellula Robotics Ltd. | Burnaby, Canada | Visit site |
| Cengiz Holding | Üsküdar, Türkiye | Visit site |
| Cenovus Energy | Calgary, Canada | Visit site |
| Central Electricity Regulatory Commission (CERC) | New Delhi, India | Visit site |
| Central Steel Build | Kyneton, Australia | Visit site |
| Centre for Sustainable Energy | Bristol, United Kingdom | Visit site |
| Centro Energy | China | Visit site |
| Centro Tecnológico EnergyLab | Vigo, Spain | Visit site |
| Centrum Wiskunde & Informatica | Amsterdam, Netherlands | Visit site |
| Centum Electronics Ltd. | Bengaluru, India | Visit site |
| Cenviro Group | Kuala Lumpur, Malaysia | 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 |
| CharIN e.V. | Berlin, Germany | Visit site |
| Chemonics Egypt Consultants | Giza, Egypt | Visit site |
| Chengdu Sixpence Technology Co., Ltd. | China | Visit site |
| Chiko Solar | Shanghai, China | Visit site |
| China Datang Corp Renewable Power Co Ltd | Beijing, China | Visit site |
| China Energy Engineering Group Co. Ltd. | Beijing, China | Visit site |
| China-Manufacturer | China | Visit site |
| Chint Cable | Bathinda, India | Visit site |
| Ciera Group | Calgary, Canada | Visit site |
| Circu Li-ion | Ludwigshafen am Rhein, Germany | Visit site |
| Circulair Friesland | Leeuwarden, Netherlands | Visit site |
| Circutor | Sabadell, Spain | Visit site |
| Citus Power | Sarıyer, Türkiye | Visit site |
| City of Amsterdam | Dunabogdány, Hungary | Visit site |
| City of Edmonton | Edmonton, Canada | Visit site |
| City of Toronto | Toronto, Canada | Visit site |
| Clamore Solar Eswatini | Mbabane, Eswatini | Visit site |
| Clean Energy Association of British Columbia (CEBC) | Vancouver, Canada | Visit site |
| Clean Energy Pipeline | London, United Kingdom | Visit site |
| CleanIQ | Komotini, Greece | Visit site |
| Cleanearth | Lashibi, Ghana | Visit site |
| Cleantech Commons™ | Peterborough, Canada | Visit site |
| ClearBlue Markets | Toronto, Canada | Visit site |
| Clemens Kraft AS | Oslo, Norway | Visit site |
| Clemessy | Mulhouse, France | Visit site |
| ClimEtSan-OnTheGround | Bonn, Germany | Visit site |
| Climacool by Blue Pearl Energy | La Boisse, France | Visit site |
| Climagea | Pomezia, Italy | Visit site |
| Climate Council | Australia | Visit site |
| Climate Group | London, United Kingdom | Visit site |
| Climate Salad | Sydney, Australia | Visit site |
| Climate Scale | Brussels, Belgium | Visit site |
| Climate X | London, United Kingdom | Visit site |
| Cloudberry Clean Energy | Karlstad, Norway | Visit site |
| Clough | Australia | Visit site |
| Clúster Energético de Nuevo León | Monterrey, Mexico | Visit site |
| Clúster de l'Energia Eficient de Catalunya | Badalona, Spain | Visit site |
| Coastwide Solar | Gold Coast, Australia | Visit site |
| Cobreflex Condutores Elétricos | Jandira, Brazil | Visit site |
| Cogenfin | Forest, Belgium | Visit site |
| Cogengreen | Namur, Belgium | Visit site |
| Cogeninfra | Borgaro Torinese, Italy | Visit site |
| Colgas | Bogotá, Colombia | Visit site |
| Columbia Basin Trust | Castlegar, Canada | Visit site |
| Com-Cavi | Avezzano, Italy | Visit site |
| ComOps B.V. | Lijnden, Netherlands | Visit site |
| ComfortZone AB | Täby, Sweden | Visit site |
| Comis S.r.l. | Pesaro, Italy | Visit site |
| Community Energy England | Sheffield, United Kingdom | Visit site |
| Compact Syngas Solutions Limited | Deeside, United Kingdom | Visit site |
| Compto Energies Renouvelables | بن عروس, Tunisia | Visit site |
| Comunità Energetiche S.p.A. | Terni, Italy | · |
| Con4Mare | Hamburg, Germany | Visit site |
| Conduct Technical Solutions | Barendrecht, Netherlands | Visit site |
| Conloop GmbH | Freiburg im Breisgau, Germany | Visit site |
| Consnant Technology | Shenzhen Shi, China | Visit site |
| Consolidated Contractors Company | Amarousio, Greece | Visit site |
| Consolidated Power Projects | Adelaide, Australia | Visit site |
| Constructiv | Brussels, Belgium | Visit site |
| Contact Solar LTD | Chorley, United Kingdom | Visit site |
| Contemporary Amperex Technology Hungary Kft. | Debrecen, Hungary | Visit site |