From Energy SG’s own, Atsumasa Sakai, this paper highlights lessons from Mongolia on how to design a grid-connected battery energy storage system (BESS) to help accommodate variable renewable energy outputs. It suggests how developing countries can address technical design challenges, such as determining storage-capacity size, and regulatory issues to do with ownership, safety, sustainability, and commercial viability. It aims to help governments accelerate BESS solutions and expedite progress toward carbon-neutral societies. Designing a Grid-Connected Battery Energy Storage System: Case Study of Mongolia