  The decarbonization of energy systems worldwide requires a transformation of
their design and operation across all sectors, that is, the residential and
commercial, industrial, and transportation sectors. Energy system models are
frequently employed for assessing these changes, providing scenarios on
potential future system design and on how new technologies and a modified
infrastructure will meet future energy demands. Thus, they support investment
decisions and policy-making. The Python-based Framework for Integrated Energy
System Assessment (ETHOS.FINE) is a software package that provides a toolbox
for modeling, analyting and evaluating such energy systems using mathematical
optimization. ETHOS.FINE is part of the Energy Transformation paTHway
Optimization Suite (ETHOS) , a collection of modeling tools developed by the
Institute of Energy and Climate Research - Techno-Economic System Analysis
(IEK-3) at Forschungszentrum J\"ulich. ETHOS offers a holistic view on energy
systems at arbitrary scales providing tools for geospatial renewable potential
analyses, time series simulation tools for residential and industrial sector,
discrete choice models for the transportation sector, modeling of global energy
supply routes, and local infrastructure assessments, among others. The ETHOS
model suite is, e.g., used for analyzing the energy transition of Germany
(Stolten et al., 2022).
