The number of smart things in our societies is booming. This trend challenges the eco design of the Internet of Things (IoT) because decisions depend on material availability for manufacturing devices, and energy for powering supporting infrastructures. So far, research has oriented much effort on local devices and instruments allowing environmental assessment like lifecycle modeling fall short against the complexity of the full IoT infrastructure. This article examines such complexity and proposes an adapted lifecycle modeling approach to sharpen the environmental evaluation and eco design of IoT systems, putting emphasis on the IoT hardware and the energy consumption of mutualized infrastructure.