Energy Policy of Poland until 2040 (PEP2040) does not take into account the ambitious goals of EU climate policy and ignores fossil fuels being pushed out by renewable energy sources. Therefore, Instrat has developed an alternative to PEP2040 for the energy mix of the National Electricity System using the PyPSA-PL model. It is based on the PyPSA open modeling environment and data from the energy.instrat.pl platform. The model features unprecedented granularity, and our methodology used in the project is based on the most current global modeling practices. The tool developed by Instrat enables optimization of the energy mix with high hourly resolution (8760 h/a) and under a range of network constraints (400 and 220 kV networks). With its help, we answer research questions about the share of individual fuels, estimate power generation costs, total system costs, load on individual lines and necessary infrastructure investments.