This paper undertakes part of the assessment of the sustainable energy security (SES) for India. SES goes beyond 'energy supply' and is a function of the aggregate energy system of a country, including the 'energy demand' and 'conversion and distribution sub-system'. The supply sub-system which consists of eight primary energy sources viz. coal, oil, natural gas, biomass, hydro, solar, wind and nuclear has been evaluated for four dimensions of SES, viz., availability, affordability, efficiency and (environmental) acceptability using 16 selected metrics. The dimensional indices are calculated for domestic and imported energy sources separately for the years 2002, 2007 and 2012. Results reveal that the SES index for oil has increased by 10% but it has decreased by 6% for gas from 2002 to 2012, while changes for other energy sources are marginal. The overall supply subsystem SES index is approximately 0.75 (against an ideal value of 1.0) which reveal the shortfall from the desired value. A sensitivity analysis reveals that the SES index is relatively robust to variation in weights. The assessment provides a comprehensive way to track the performance of the energy supply sub-system and can be used to design policy interventions for improving the overall SES index for India.