Energy efficiency is crucial for battery-powered devices in constrained networks, especially in Smart Agriculture and Smart Cities scenarios. To maximize battery life and ensure secure communications, lightweight key exchange protocols like Ephemeral Diffie–Hellman Over COSE (EDHOC) are essential. To further optimize energy efficiency, EDHOC can be combined with the Static Context Header Compression (SCHC) protocol, which is designed to compress and fragment data packets. This work demonstrates that EDHOC and SCHC can be successfully integrated to establish secure session keys in Internet of Things (IoT) scenarios. The attained results showcase that security mechanisms can be implemented in resource-limited devices with minimal energy impact, extending battery life. The experiments showed it is possible to compress the EDHOC exchange messages up to a ∼54% and to reduce the energy consumption by a ∼20%, while maintaining the CPU time levels in a cost-effective way. By designing IoT devices with these directives, it is possible to reduce the overall environmental footprint and increase the devices’ operational lifespan.