 The integration of renewable energy and optimization of energy used through modern technologies like IoT are crucial for sustainable energy transitions and mitigating climate change. IoT can improve energy efficiency, increase the share of renewable energy, and reduce environmental impacts in energy systems, particularly smart grids. Enabling technologies such as cloud computing and data analysis platforms are discussed, along with challenges like privacy and security, which can be addressed through solutions like blockchain technology. This survey provides an overview for energy policymakers, economists, and managers on the role of IoT in optimizing energy systems. This article was authored by Nasir Hossain Motlak, Masa Mohamedrazii, Julian Hunt, and others.