| C&D Clean Energy | Nanjing Shi, Jiangsu | Visit site |
| C&D Emerging Energy | Fujian | Visit site |
| C&I Engineering | Louisville, Kentucky | Visit site |
| C&O Sales | Lenexa, Kansas | Visit site |
| C-Green | Solna, Stockholm | Visit site |
| C-Power | Charlottesville, Virginia | Visit site |
| C2 Group - San Diego | San Diego, California | Visit site |
| CAEC | Prattville, Alabama | Visit site |
| CANEX Aluminum | 6th of October, Giza | Visit site |
| CANOVI COPERTURE SRL | Modena, Modena | Visit site |
| CAPA intelligence | Melbourne, Victoria | Visit site |
| CARMA Corp. | Lindsay, Ontario | Visit site |
| CAT Electric | Salt Lake City, Utah | Visit site |
| CATENA SERVICES S.R.L. | Osimo, Ancona | Visit site |
| CATL | Yibin | Visit site |
| CC Electrical & Renewables Ltd | Thetford, England | Visit site |
| CCAM - Commonwealth Center for Advanced Manufacturing | Disputanta, Virginia | Visit site |
| CDC Biodiversité | Paris, Île-de-France | Visit site |
| CDC Group plc | London, England | Visit site |
| CDWE | 臺北市, Taipei | Visit site |
| CE+T | Duluth, Georgia | Visit site |
| CEART.io | New York, New York | Visit site |
| CECEP Solar | Jiangsu | Visit site |
| CEEG | Nanjing Shi, Jiangsu | Visit site |
| CEFEM INDUSTRIES | · | Visit site |
| CEN Solutions | Dos Hermanas, Seville | Visit site |
| CENIMAT | i3N | · | Visit site |
| CENTER FOR ANALYSIS AND DEVELOPMENT OF EFFECTIVE POLICIES (CADEP) | Kyiv, Kyiv | Visit site |
| CEPEMAR | Vitória, Espírito Santo | Visit site |
| CER Italia | Lucca, Lucca | Visit site |
| CERESS | Comunità Energetiche | Mozzo, Bergamo | Visit site |
| CF Solar | Fayetteville, North Carolina | Visit site |
| CFR Engineering Consultants, Inc. | Germantown, Maryland | Visit site |
| CFRIEND ELECTRIC (KUNSHAN) CO.,LTD. | Kunshan, Jiangsu | Visit site |
| CFS Engineering, DPC | New York, New York | Visit site |
| CG SEMI Private Limited | Ahmedabad, Gujarat | Visit site |
| CGS | Amsterdam, North Holland | Visit site |
| CHANGYUAN TECHNOLOGY GROUP（CYG） | Shenzhen Shi, Guangdong | Visit site |
| CHANGZHOU LEMENG PRESSURE VESSEL CO..LTD | Changzhou City, Jiangsu Province | Visit site |
| CHG EnSOL | Waipahu, Hawaii | Visit site |
| CHINA GWELL CO.,LTD. | Taicang, Suzhou, Jiangsu Province | Visit site |
| CIEL Group | Lontzen, Liege | Visit site |
| CIEL Solar SA | Romanel-sur-Lausanne, Vaud | Visit site |
| CINDA ENGINEERING & CONSTRUCTION PRIVATE LIMITED | Noida, Uttar Pradesh | Visit site |
| CITROBOX ENERGIAS | Darmstadt, Hesse | Visit site |
| CJK | The Ward, County Dublin | Visit site |
| CJR Renewables | Leça do Balio, Porto | Visit site |
| CJR-Cândido José Rodrigues | Selho, Braga | Visit site |
| CL Construction, LLC | Lincoln, Nebraska | Visit site |
| CLEAN ENERGY FUND OF THE CAROLINAS | Raleigh, North Carolina | Visit site |
| CLEAN-Air(Africa) | Nairobi, Nairobi | Visit site |
| CLHYNN | Besançon, Doubs | Visit site |
| CM Solar | San Diego, California | Visit site |
| CMBlu Energy | Alzenau, Bavaria | Visit site |
| CMEC 中东区域公司 | Dubai, Dubai | Visit site |
| CMI (Central Moloney) | Pine Bluff, Arkansas | Visit site |
| CMS Albiñana & Suárez de Lezo | Madrid, Madrid | Visit site |
| CMS SURVEYORS | Sydney, New South Wales | Visit site |
| CMTA, Inc. | Louisville, Kentucky | Visit site |
| CNR (Compagnie Nationale du Rhône) | Lyon, Rhône | Visit site |
| CNR Construction | Pleumeleuc, Ille-et-Vilaine | Visit site |
| CNTE | Fujian | Visit site |
| CNTSUN | Hubei | Visit site |
| COGECLIM | Île-de-France | Visit site |
| COLLADO ENGINEERING | White Plains, New York | Visit site |
| COMBATT S.A. | Athina, Attica | Visit site |
| CONGEOCON | São Paulo, São Paulo | Visit site |
| CONSEJO DE PROFESIONALES EN ENERGÍA FOTOVOLTAICA - CPEF | San José del Castillo, Jalisco | Visit site |
| CONSGA BIC SAS | Bogotá, Bogotá | Visit site |
| CONSTRUCCIONES RUBAU | Barcelona, Barcelona | Visit site |
| CONVERDAN A/S | Vojens, Southern Denmark | Visit site |
| COPA-DATA | Salzburg, Salzburg | Visit site |
| CORE Geomatics | Calgary, Alberta | Visit site |
| CORE Safety Group | Chattanooga, Tennessee | Visit site |
| CPB Contractors | Sydney, New South Wales | Visit site |
| CPD Powerline Ltd | Armagh, Northern Ireland | Visit site |
| CPM Engenharia - 35 anos | Vila Velha, Espírito Santo | Visit site |
| CPS America | Pleasanton, California | Visit site |
| CPower Energy | Stevenson, Maryland | Visit site |
| CR2P Photovoltaïque | Saint-Paul-lès-Dax, Landes | Visit site |
| CRE - Commission de régulation de l'énergie | Paris, Île-de-France | Visit site |
| CREC - Clúster de Residus de Catalunya | Barcelona, Barcelona | Visit site |
| CRU | London, England | Visit site |
| CS Energy | Edison, New Jersey | Visit site |
| CS Instruments Turkey | Pendik, Istanbul | Visit site |
| CSA Group | Etobicoke, Ontario | Visit site |
| CSD Energy Advisors is Now Environ Energy | New York, New York | Visit site |
| CSG Developers | New Bedford, Massachusetts | Visit site |
| CSG Energy | Guangzhou Shi, Guangdong | Visit site |
| CSI Electrical Contractors, Inc. | Santa Fe Springs, California | Visit site |
| CST Energy | Chiva, Valencia | Visit site |
| CTCI | 臺北市, Taipei | Visit site |
| CTECHi | Burk's Falls, Ontario | Visit site |
| CTS Builders | New York, New York | Visit site |
| CU Strategic Planning | Tacoma, Washington | Visit site |
| CUPERTINO ELECTRIC | Novato, California | Visit site |
| CV International | Norfolk, Virginia | Visit site |
| CW ENERJİ | Döşemealtı, Antalya | Visit site |
| CW Energy | Shepherd, Texas | Visit site |
| CWHI (CNOOD-Wenchong Heavy Industries) | Guangzhou Shi, Guangdong | Visit site |
| CWP Energy | Frodsham, England | Visit site |
| CWP Global | Singapore, South West Community Development Council | Visit site |
| CYSORE | León, Guanajuato | Visit site |
| CZM Foundation Equipment | Ellabell, Georgia | Visit site |
| CZT Energy | Sealy, Texas | Visit site |
| Cables RCT | Zaragoza, Zaragoza | Visit site |
| Cableworld | Bolton, England | Visit site |
| Cabur | Altare, Savona | Visit site |
| Cadeo | Half Moon Bay, California | Visit site |
| Cadivi | Đà Lạt, Lâm Đồng | Visit site |
| Cadre AS | Kristiansand, Agder | Visit site |
| Cairn Risk | Glasgow, Scotland | Visit site |
| Cajun Industries, LLC | Baton Rouge, Louisiana | Visit site |
| CalWave Inc. | Oakland, California | Visit site |
| Calderys | Paris, Île-de-France | Visit site |
| Calibrant Energy | Tampa, Florida | Visit site |
| California Building Officials | Sacramento, California | Visit site |
| California Department of Forestry and Fire Protection (CAL FIRE) | Sacramento, California | Visit site |
| California Energy Commission | Sacramento, California | Visit site |
| California Governor's Office of Business and Economic Development (GO-Biz) | Sacramento, California | Visit site |
| California Public Utilities Commission | San Francisco, California | Visit site |
| Calik Holding | Şişli, Istanbul | Visit site |
| Call2Recycle, Inc. | Atlanta, Georgia | Visit site |
| Calor Energy | Charlotte, North Carolina | Visit site |
| Caltech Group | Calgary, Alberta | Visit site |
| Caltrans | Sacramento, California | Visit site |
| Camber Energy, Inc. | Houston, Texas | Visit site |
| Cambridge GaN Devices Ltd | Cambridge, England | Visit site |
| Camco | London, England | Visit site |
| Camille Bauer Metrawatt AG | Wohlen, Aargau | Visit site |
| Campbell County VA Economic Development | Rustburg, Virginia | Visit site |
| Campbell Scientific | Logan, Utah | Visit site |
| Canadian Climate Institute / Institut climatique du Canada | Bobcaygeon, Ontario | Visit site |
| Canadian Hydrogen Association (CHA) | Vancouver, British Columbia | Visit site |
| Canadian Solar | Guelph, Ontario | Visit site |
| Canadian Steel Producers Association (CSPA) | Ottawa, Ontario | Visit site |
| Canbat | Vancouver, British Columbia | Visit site |
| Cando Solar | Jiangsu | Visit site |
| Cangzhou Juntong Hardware Products Co.,Ltd. | Cangzhou | Visit site |
| Canoe | Stavanger, Rogaland | Visit site |
| Canopy Cameroun SARL | Yaounde, Centre | Visit site |
| Canopy Power | Singapore, South West Community Development Council | Visit site |
| Cantor Fitzgerald | New York, New York | Visit site |
| Cantsink Manufacturing | Lilburn, Georgia | Visit site |
| Capacitech Energy | Orlando, Florida | Visit site |
| Capcora | Frankfurt am Main, Hesse | Visit site |
| CapeZero | New York, New York | Visit site |
| Capgemini Invent | Paris, Île-de-France | Visit site |
| Capital Energy, LLC | Tempe, Arizona | Visit site |
| CapitalOne Energy, Inc. | Pasig, Pasig | Visit site |