Abstract: Effective emergency communication between citizens and authorities after a power outage can be a challenging task. In such situations, citizens may be in danger and need to contact authorities in case of an emergency. However, overloaded cellular networks and failing network infrastructure can severely hamper citizens' ability to communicate with authorities, even if their smartphones are still functioning. Addressing these challenges requires the development of effective post-blackout communication systems that can operate in a range of emergency scenarios. In this work we investigate smartphone state of charge during the day in order to evaluate the impact of a power outage on the citizens ability to communicate in a post-blackout scenario. The results are then used to propose future-proof communication networks that are suitable for post-blackout emergency communication especially after cellular network infrastructure has failed. We introduce two post-blackout communication phases named communication-burst and communication-void. Our study indicates that a significant amount of smartphones remain usable even after a long-lasting blackout and communication infrastructure failure. Not utilizing these devices could lead to missed opportunities for emergency communication