Ensuring the provision of energy at all times and places is a challenge for energy systems with a large share of variable renewable energy sources (RES). The issue is the subject of heated public debate, with reasoned arguments highlighting both the advantages and limitations of these sources. However, balancing these arguments – that is, answering the question of whether RES can plausibly have a significant share in the Polish energy mix – requires a more comprehensive analysis using tools suitable for this purpose. The PyPSA-PL model, being developed by Instrat, is just such a tool.