Access to reliable and affordable energy is vital for sustainable development. In the off-grid areas of developing countries, decentralized energy solutions have received increasing attention due to their contributions to reducing poverty. However, most of the rural population in many developing countries still has little or no access to modern energy technologies. This paper assesses the factors that determine the successes and failures of decentralized energy solutions based on local harmonized case studies from heterogeneous contexts from Asia, sub-Saharan Africa, and South America. The case studies were analyzed through the coupled lenses of energy transition and the Water–Energy–Food Security (WEF) Nexus. The findings indicate that access to modern decentralized energy solutions has not resulted in complete energy transitions due to various tradeoffs with the other domains of the WEF Nexus. On the other hand, the case studies point at the potential for improvements in food security, incomes, health, the empowerment of women, and resource conservation when synergies between decentralized energy solutions and other components of the WEF Nexus are present.