Development of a Low Cost IoT Based Energy Monitoring System for Smart Urban Buildings in Developing Countries

This paper presents the design and implementation of a low-cost IoT-based energy monitoring system for small and medium-sized buildings in developing countries. The system integrates an ESP32 microcontroller, ACS712 current sensors, and a ZMPT101B voltage sensor to measure real-time electrical parameters including voltage, current, power, and energy consumption. Data is transmitted using the MQTT protocol to a cloud-based platform for visualization and analysis. A prototype system was deployed in a three-room office building in Phnom Penh, Cambodia, over a 30-day period. Experimental results demonstrate measurement accuracy of ±1.8% for current and ±0.9% for voltage, with end-to-end data latency below 1.2 seconds. The total hardware cost per monitoring node is approximately USD 22, representing a reduction of over 85% compared to commercial systems. The system successfully identified energy waste patterns with a potential cost saving of 18–22% per month. This study demonstrates that affordable IoT-based solutions can significantly improve energy efficiency and support sustainable infrastructure development in resource-constrained environments.