Despite signicant advancements in green IoT design frameworks aimed at minimizing energy consumption, extending node lifetimes, reducing carbon footprints, and enhancing sustainability, energy losses due to imperfections in energy storage systems (ESS)such as batteries, capacitors, and supercapacitorsremain a critical challenge. These ineciencies degrade the overall energy performance of IoT nodes and must be carefully accounted for in energy-ecient system design. This paper analyzes the impact of ESS non-idealities on green IoT nodes, focusing on energy leakage and its eects on key performance metrics, including service outage probability, node lifetime distribution, and the time-dependent mean number of energy packets (EPs) in the ESS. To mitigate energy losses from leakage, we explore two key strategies: (i) Enhancing energy generation by increasing energy harvester capacity (e.g., deploying additional solar panels or higher-eciency alternatives). (ii) Reducing energy consumption by implementing ESS energy thresholds that transition nodes into low-power states when energy levels drop below predened limits. By addressing ESS imperfections and optimizing energy management strategies, this work aims to enhance the sustainability, reliability, and eciency of green IoT nodes by analyzing the interplay between energy leakage, workload-driven energy demand, and photovoltaic energy harvesting.