India has achieved near-universal electrification, yet large inequalities persist in the reliability of the electricity supply. Combining high-resolution satellite-based measures of electricity reliability—defined as the share of nights with detectable illumination—with village-level census data, this paper shows that reliability remains systematically unequal across social groups. While Scheduled Caste villages largely track district-level reliability, Scheduled Tribe (ST) villages face a pronounced enclave penalty. Homogeneous ST enclaves (ST population ≥90%) exhibit 10.7 percentage points fewer illuminated nights than otherwise comparable villages within-district with low ST shares. We further identify a mobility trap: homogeneous ST enclaves are about 16.6 (16.0) percentage points more likely to remain energy poor in 2012 (2019) and 11.7 percentage points less likely to escape energy poverty between 2012 and 2019. These findings suggest that as access becomes universal, infrastructure exclusion increasingly operates through a less visible rationing of service quality in socially homogeneous tribal settlements.