We measure firm-level productivity changes in the Indian electricity sector during a period that witnessed several pro-market regulatory changes. Using information collected from multiple sources we construct a unique panel of generating firms and transmission and distribution utilities spanning the years 2000 to 2009. We employ a recently developed improvement in the Stochastic Frontier panel method that allows controlling for time-invariant unobserved heterogeneity. Using the method we jointly estimate inefficiency and exogenous determinants of inefficiency. We estimate a flexible translog production model and compute decomposition of productivity into components of changes in technology, efficiency, scale and price effect. During this period, especially post Electricity Act 2003, we observed a general decline in firm-level productivity at the mean rate of -1.6% per year. A positive and large technical change is observed in the sector at the rate of 8% per year, attributable possibly to newer capacity addition. Except for smaller gas based generators, inefficiency is observed to be increasing at the mean rate of 3.1% per year in the sector. Consistent with extant findings we also document no significant impact of un-bundling on firm-level efficiency.     Keywords: India's Electricity Sector Reform, Stochastic Frontier Analysis, Total Factor Productivity, Firm-Level Panel Data