| Abbreviation | Definition |
|---|---|
| IREP | Infinitus Renewable Energy Park |
| IRMIS | International Radiation Monitoring Information System |
| ISE | Institute of Sustainable Energy |
| ISEA | Illinois Solar Energy Association |
| ISEA | Irish Solar Energy Association |
| ISEER | Indian Seasonal Energy Efficiency Ratio |
| ISEO | International Sustainable Energy Organization |
| ISEP | Institute for Sustainable Energy Policies |
| ISEP | Islington Sustainable Energy Partnership |
| ISER | Infrastructure Security and Energy Restoration |
| ISES | International Student Energy Summit |
| ITER | International Thermonuclear Energy Reactor |
| ITES | International Tidal Energy Summit |
| IVDEFFUC | Integrating Vector Dimensional Energy-Force Field Unification Constant- As is considered a "One |
| IWEA | Illinois Wind Energy Association |
| IWEA | International Wind Energy Academy |
| IWEA | Iowa Wind Energy Association |
| IWEA | Irish Wind Energy Association |
| IWEC | International Weather for Energy Calculation |
| IWEC | Iran Wind Energy Conference |