The advances towards IoT systems with increased autonomy support improvements to existing applications and open new perspectives for other application domains. However, the design of IoT systems is challenging, due to the multiple design aspects that need to be considered. Connectivity and storage aspects are amongst the most significant ones, as IoT devices are resource-constrained and in many cases battery-powered. On top of them, it is also essential to consider privacy and security aspects that are linked to the protection the IoT system, as well as of the data exchanged through its connectivity interfaces. Ensuring security in an IoT system, though, is an evident need and a complex challenge, due to its impact in the battery lifetime. In this paper, we propose a methodology to manage energy consumption through a model-based approach for the energy characterization of IoT design aspects using the BIP (Behavior, Interaction, Priority) component framework. Our approach is exemplified based on an Intelligent Transport System (ITS) that uses Zolertia Zoul devices placed in traffic lights and road signs to broadcast environmental and road hazard information to crossing vehicles. The results allow to find a feasible design solution that respects battery lifetime and security requirements.