Comparative Analysis on Energy Consumption of the CoAP, HTTP, and MQTT Protocols for Resource-Constrained IoT Applications

IoT platforms often rely on resource-constrained devices with specific requirements for efficient resource utilization. Wireless communication, reduced form factor, and low power consumption are key factors for a successful IoT deployment. In the context of energy requirements, this paper examines the energy consumption of three widely used communication protocols: Constrained Application Protocol (CoAP), Hypertext Transfer Protocol (HTTP), and Message Queue Telemetry Transport (MQTT) in resource-constrained IoT applications. Firstly, existing studies are explored to understand the characteristics, architecture, and performance of the protocols. Secondly, the main aspects of each protocol are highlighted. Then, a study methodology is proposed to evaluate current consumption by comparing the secure and insecure versions of these protocols using a standardized 10-byte payload. The tests are performed under two signal levels (high and low) to assess their effect on energy consumption. The findings of this study indicate that while unencrypted MQTT QoS 0 is the most energy-efficient baseline, the introduction of cryptographic security layers imposes a severe energy penalty. Secure HTTP exhibited exponentially higher energy usage due to the computational overhead of TLS handshakes, whereas Secure MQTT QoS 0 remained the most efficient among the encrypted options. Furthermore, the results demonstrate that adverse signal conditions tend to increase energy consumption, emphasizing the critical trade-off between robust security, communication reliability, and energy autonomy in constrained IoT devices.