Energy-related training is much needed for SIDS to achieve sustainable development goals and reduce energy poverty. Online learning enables innovative formats of practice-centered trainings that address local needs and help overcome geographic constraints by efficiently reaching learners on remote islands. To justify high course production costs, content must be re-usable and the instructional design must match participants' motivation, skills, capacity, and constraints. An interdisciplinary university research cooperation used SIDS survey data to develop a learner-driven, collaborative online course for energy practitioners. Problem-based learning and peer-review mechanisms were used to localize knowledge and to practice real-world skills; sustainable institutional structures assure future iterations. The pilot reached a heterogeneous audience of 1,000 learners, geographically dispersed across the main SIDS regions. Principles of learning design outlined by the authors may also be valuable for capacity-building with geographically dispersed, heterogeneous learners beyond SIDS.