The study focuses on evaluating off-grid community systems in Tanzania, aiming to assess their reliability over time. The study employs a Difference-in-Differences (DiD) econometric model to analyse the impact of off-grid community systems on reliability, utilising data from multiple communities across Tanzania. A notable finding is that the DiD model effectively captures system reliability changes over time in Tanzanian communities, with significant improvements observed in post-intervention periods compared to pre-intervention phases. The DiD method provides robust estimates of system reliability in off-grid community systems across Tanzania, offering valuable insights for policymakers and stakeholders. Policymakers should consider the DiD model as a reliable tool for assessing the impact of off-grid energy initiatives on reliability. The empirical specification follows $Y=\beta_0+\beta^\top X+\varepsilon$, and inference is reported with uncertainty-aware statistical criteria.