The City-based Optimization Model for Energy Technologies (COMET-NYC) is an energy system modeling tool developed by the U.S. Environmental Protection Agency. COMET is applied to New York City to support long-term, metropolitan-scale air, climate, and energy planning. Built on the internationally recognized TIMES modeling framework, COMET-NYC identifies the least-cost mix of technologies and fuels required to meet projected energy demands from 2010 to 2055 across NYC’s buildings, transportation, and electricity sectors. COMET-NYC uses a scenario-based optimization approach to simulate the deployment of energy technologies under various assumptions, policies, and constraints. It incorporates local data sources to estimate and calibrate energy consumption and emissions at the borough level. It tracks both greenhouse gases (GHGs) and criteria air pollutants, supporting city-level climate and air quality policy evaluation. The model includes detailed modules for the residential, commercial, industrial, and transportation sectors, accounting for current and future technology costs, fuel types, and efficiency parameters. It uses linear programming to minimize system-wide costs while meeting energy service demands and emissions targets. COMET-NYC supports both retrospective analysis (e.g., calibration to 2010, 2015, and 2020) and future scenario exploration, such as electrification strategies. Two versions of the model are included in this dataset: v15.0.9, which underpinned emissions reduction planning during the 2023–2024 NYC budgeting cycle, and v16.0.1, which includes updated buildings data and improved calibration. The documentation included various appendices for background data to build COMET-NYC. Appendix A through F are included in this dataset. Appendix A provides time slice documentation; Appendix B provides PLUTO 2010 data; Appendix C provides original 2014 building end-use demand splits for NYC; Appendix D provides EIA 2023 building technology data; APPENDIX E provides 2015 NYMTC SEDS population and employment forecasts; and APPENDIX F provides Documentation of Transportation Sector Emission Factors Updates and related input datasets for MOVES model. This dataset is associated with the following publication: Kaplan, O., Z. Carroll, M. Pied, R. Chaffanjon, and K. Vaillancourt. Documentation for application of City-based Optimization Model for Energy Technologies (COMET) to New York City to support metropolitan-scale air, climate, and energy planning. U.S. Environmental Protection Agency, Washington, DC, USA, 2025.