<p>The Internet of Things (IoT) has become incorporated into our daily lives. Since IoT has been used in a variety of sectors such as healthcare, smart cities, and agriculture, this rapidly developing trend brings challenges and creates new requirements. The software and hardware domains offer more opportunity to successfully deploy the Internet of Things in all aspects of our lives. By focusing on the operating system domain, we expect to improve the use of IoT devices and make them more energy efficient in this article. Initially, we conducted a thorough study of the documents to assess the big picture, from key features to details about IoT operating system platforms. While various techniques exist for reducing power consumption in constrained, low-end devices, determining the most effective approach necessitates substantial research, measurement, and testing. To that purpose, we collected data on the power consumption of Real-Time Operating Systems (RTOSs) and determined the best choices by evaluating their IoT-relevant characteristics. We primarily focus on open-source operating systems with real-time capabilities as the basis for anticipated future practical trials.</p>