Off-grid communities in Tanzania rely on various energy systems for lighting, cooking, and other essential services. There is a need to evaluate these systems' efficiency to inform policy and improve community welfare. A mixed-methods approach combining quantitative data analysis with qualitative interviews was employed. The study utilised a difference-in-differences (DiD) model to compare pre- and post-intervention performance of off-grid energy systems. The DiD model showed an average efficiency gain of 25% in the intervention group compared to controls, indicating significant improvements in system reliability and cost-effectiveness. This quasi-experimental design provided robust evidence for assessing the effectiveness of off-grid community energy systems, contributing to better policy decisions and resource allocation. Policy makers should prioritise investments in off-grid energy systems that demonstrate efficiency gains through rigorous evaluation methods. Off-Grid Communities, Quasi-Experimental Design, Efficiency Gains, Difference-in-Differences (DiD), Energy Systems The empirical specification follows $Y=\beta_0+\beta^\top X+\varepsilon$, and inference is reported with uncertainty-aware statistical criteria.