| Term | Definition / Meaning / Stand for |
| SPP |
Small Power Producer |
| SSRV |
Solar Sail Race Vehicle |
| STEG |
Solar Thermal Electricity Generation |
| STIG |
Steam Injected Gas Turbine |
| SWPS |
Solar Water Pumping System |
| T&D |
Transmission and Distribution |
| TAC |
Total Active Capacity |
| TBTU |
Trillion British Thermal Unit |
| TE |
Thermal Efficiency |
| TEEP |
The Energy Experimenting People |
| TLC |
Total Load Control |
| TMI |
Three Mile Island |
| TNUoS |
Transmission Network Use of System |
| TPSL |
Tidal Power Scotland Limited |
| TRTP |
Tehachapi Renewable Transmission Project |
| TSP |
Total Suspended Particles |
| TTR |
Transmission Tower Rework |
| UCA |
Utility Control Algorithm |
| UCB |
Undersea Cable Bundle |
| UCGS |
Underground Coal Gasification System |
| UDB |
Utility Data Base |
| UIA |
Utility Impact Assessment |
| UIG |
Uninterruptible Gas Supply |
| USG |
United States Geological Survey (energy-related research) |
| UVR |
Ultravioleta Ray (used in solar energy) |
| UWT |
Underground Water Treatment |
| VAC |
Voltage Alternating Current |
| VAP |
Voltage Adjustment Point |
| VDC |
Voltage Direct Current |
| VFC |
Voltage Frequency Converter |
| VIC |
Voltage Isolation Converter |
| VOR |
Voltage Overload Relay |
| VPT |
Voltage Protection Technology |
| VRT |
Voltage Regulation Technology |
| VSC |
Voltage Source Converter |
| VSI |
Voltage Stability Index |
| VSTF |
Voltage Source Transmission Function |
| WAC |
Wind Action Coefficient |
| WEC |
Wind Energy Conversion |
| WFA |
Wind Flow Assessment |
| WFM |
Wind Farm Management |
| WPI |
Wind Power Integration |
| WSS |
Wind Speed Sensor |
| WTA |
Wind Turbine Array |
| WTS |
Wind Turbine Simulator |
| WTT |
Well-to-Tank (energy efficiency measure) |
| XAI |
Xenon Artificial Intelligence (used in energy optimization technologies). |
| XHT |
Xenon High-Temperature (used in energy studies, such as ion propulsion). |
| XIBL |
X-ray Imaging Beamline (used in energy materials research). |
| XLO |
X-ray Light Optics (used in focusing X-rays for energy material research). |
| XMM-Newton |
A satellite used in astrophysical energy studies. |
| XRD |
X-ray Diffraction (used to analyze crystalline structures of materials related to energy storage and conversion). |
| XRN |
Xenon Radiator Network (used in nuclear and radiation-related energy studies). |
| XTA |
X-ray Transmission Analysis (used for energy system diagnostics). |
| YAG |
Young American Green (programs involving young people in clean energy and environmental protection) |
| YCN |
Youth Climate Network (a network of youth focusing on the climate crisis and energy solutions) |
| YED |
Youth for Energy Development (youth programs aimed at development in renewable energy) |
| YFP |
Young Future Planners (a group focusing on future energy planning, especially in renewable energy) |
| YGA |
Youth for Green Alternatives (youth-focused advocacy for green and sustainable energy) |
| YIE |
Young Innovators in Energy (youth-driven innovations in energy technology) |
| YTF |
Year-To-Fuel (used in energy consumption reporting, particularly in renewable energy contexts) |
| ZAT |
Zero Asset Threshold (used in energy finance or investment strategies aiming for no asset-related environmental impact) |
| ZCC |
Zero Carbon Certificate (a certification for products or companies that are carbon neutral or have net-zero emissions) |
| ZDO |
Zero Discharge Operations (operations in energy production with no waste discharge) |
| ZFS |
Zero Fuel Source (used in reference to energy sources that do not require fossil fuels) |
| ZGT |
Zero-Greenhouse Technology (technologies in energy generation that produce no greenhouse gases) |
| ZLS |
Zero-Lead Standards (used in energy efficiency standards related to reducing harmful materials) |
| ZLV |
Zero Landfill Volumes (related to reducing waste in energy production or consumption) |
| ZVRT |
Zero Volatile Renewable Technology (a renewable technology with no volatility or instability) |
| rdSAP |
Reduced Data Standard Assessment Procedure |