How does increasing complexity affect the vulnerability or resilience of critical infrastructures? The TA preliminary study discusses why and how an in-depth examination of the complexity of our energy system can help to make our critical infrastructures more resilient. It also identifies topics that lend themselves to in-depth analysis. These include analysing systemic risks from solar storms, the use of artificial intelligence, the raw material and supplier dependencies that can result from an increasingly complex energy system, and ensuring the functionality of critical energy infrastructures under changing climatic conditions.