| U Logistique | Carquefou, Loire-Atlantique | Visit site |
| U-Energy | Abu Dhabi, Abu Dhabi | Visit site |
| U.I. Lapp | Stuttgart, Baden-Württemberg | Visit site |
| U.S. Department of Energy (DOE) | Washington, District of Columbia | Visit site |
| U.S. Department of Transportation | Washington, District of Columbia | Visit site |
| U.S. Department of the Interior | Washington, District of Columbia | Visit site |
| U.S. Geological Survey (USGS) | Reston, Virginia | Visit site |
| UES | Orlando, Florida | Visit site |
| UFP Packaging | Grand Rapids, Michigan | Visit site |
| UGREEN MEA | Parauapebas, Pará | Visit site |
| UK Energy Research Centre (UKERC) | London, England | Visit site |
| UK Metering | Mansfield, England | Visit site |
| UKAI S.A. | Bilbao, Biscay | Visit site |
| UKRAINIAN HYDROGEN ASSOCIATION | Kyiv, Kyiv | Visit site |
| UKSOL | Gerrards Cross, England | Visit site |
| UL Research Institutes | Evanston, Illinois | Visit site |
| UL Solutions | Northbrook, Illinois | Visit site |
| UNIGRID Battery | San Diego, CA | Visit site |
| UNINOVA | Caparica, Setúbal | Visit site |
| UP Catalyst | Tallinn, Harju | Visit site |
| UPS Solar | Preston, England | Visit site |
| UPSEN | Shenzhen Shi, Guangdong | Visit site |
| US Floating Solar | Weston, West Virginia | Visit site |
| US Helicals | Gainesville, Texas | Visit site |
| USA DAELIM TRANSFORMER | Houston, Texas | Visit site |
| UTICA® Singapore | Singapore, Central Singapore Community Development Council | Visit site |
| UUGreenPower Co., Ltd | 新竹市, Hsinchu City | Visit site |
| UZ ENERGY LIMITED | Shenzhen Shi, Guangdong | Visit site |
| Ubetter Technology | Shenzhen Shi, Guangdong | Visit site |
| Uflex Divisione Energia | Busalla, Genoa | Visit site |
| Uhome | Wuxi Shi, Jiangsu | Visit site |
| Ulica Solar | Ningbo Shi, Zhejiang | Visit site |
| Ulteig | Fargo, North Dakota | Visit site |
| Una Terra Early Growth Fund | Zürich, Zürich | Visit site |
| Unearthly Materials | Rochester, New York | Visit site |
| UniSource Energy Services | · | Visit site |
| Unico LLC | Franksville, Wisconsin | Visit site |
| Unicorn Factory Lisboa | Lisboa, Lisbon | Visit site |
| Unified GlobalTech (I) Pvt Ltd | Bengaluru, Karnataka | Visit site |
| Unik Batteries | Pimpri-Chinchwad, Maharashtra | · |
| Unika | Beşiktaş, Istanbul | Visit site |
| Unimacts Global | Sloan, Nevada | Visit site |
| Unione Geotermica Italiana (UGI) | Pisa, Pisa | Visit site |
| Unirac, Inc. | Albuquerque, New Mexico | Visit site |
| Unisun Energy Europe | Rotterdam, South Holland | Visit site |
| Unisun Power Solutions Pvt Ltd | Mumbai, Maharashtra | Visit site |
| Uniteck | Bakersfield, California | Visit site |
| United ECO-Technology Corp. | Alexandria, Virginia | Visit site |
| United Rentals | Stamford, Connecticut | Visit site |
| Unlimit Energy Inc | Walnut, California | Visit site |
| Unlimited Solar | Virginia Beach, Virginia | Visit site |
| Unoenergy Green Solutions Spa | Castelnuovo Rangone, Modena | Visit site |
| UpLink – World Economic Forum | Genève, Geneva | Visit site |
| Upowa | Johannesburg, Gauteng | Visit site |
| Uppteam | Ormond Beach, Florida | Visit site |
| Upstart Power | Southborough, Massachusetts | Visit site |
| Urban Grid | Houston, Texas | Visit site |
| Urja | Zürich, Zürich | Visit site |
| Ursa Space Systems | Ithaca, New York | Visit site |
| Uría Menéndez | Bilbao, Biscay | Visit site |
| Utopia | Dublin, County Dublin | Visit site |