The global diffusion of renewable energy technology (RET) has been sluggish, and as a result governmental support and policy interventions have been required. In this paper, we empirically investigated an innovation system building practice of an organisation engaged in the diffusion of solar home systems in developing countries. The study shows how a technological innovation system (TIS) can be built from scratch by a key actor in a developing country setting. Besides making a scholarly contribution to the TIS literature by proposing a system building framework, the study outlines required policy interventions mainly in looking for, promoting, and enhancing practices of system builders for RET diffusion in less developed economies.