Apart from international scale, also for (sub)-national energy system planning, international effects exist, that have a direct influence on local regions The concept of Nationally tailored energy system models account for these effects as a new approach embedding a national energy system model into a multi-regional context. For Austria, with PyPSA-AT a fully sector-coupled nationally tailored energy system model is currently under development. It is fully open source, relies on open data. and is technically integrated into the existing pypsa-ecosystem. https://github.com/AGGM-AG/pypsa-at https://github.com/maxnutz/pypsa_validation_processing https://github.com/maxnutz/eurostat-energy-balance_processing